Mar 19 2013

Single Page Applications 2: Validation Error Handling

Category: MVC | Asp.netFrancesco @ 22:30

Data Moving Plugin Controls

Data Moving Plugin Styling

Data Moving Plugin Forms: Detail Views, Data Filtering UI, and Undo/Redo Stack

Single Page Applications 1: Manipulating the Client Side ViewModel

Single Page Applications 2: Validation Error Handling

Single Page Applications 3: TreeIterator

This is the second half of the tutorial Single Page Applications 1: Manipulating the Client Side ViewModel that describes the enhancements added to the standard asp.net Mvc validation error engine by the Data Moving Plug-in. We advice to assist the video associated to this introductory tutorial before reading it:

In the Data Moving Plug-in validation rules, and error handling are coded with the usual tools of Asp.net Mvc, such as Data Annotations (or Fluent validation), by adding errors to the ModelState, etc. Also client side validation is based on the jquery validation plug-in. However, all this tools have been enhanced in several ways. First of all, server errors are returned also as a result of JSon updates, and dispatched to the right places in the UI (thanks to the updatesManagers that handle the updates). Moreover, also elements that are detached from the Dom, and rendered again by instantiating  client templates “remember” their error state thanks to parallel data structures that takes care of this “job”.

Probably, the more interesting enhancement is “error bubbling”. What is “error bubbling”? Suppose you need to report an error to the property AllProgrammers[1].EMail, that is to the Email of the second programmer of the programmers list. Well, since the grid has no visible Email column, the error cant be shown! In order to overcome this problem the error is bubbled up to the whole entity level:  AllProgrammers[1]. Now since we added an error column to the programmers grid the user can see the second programmer has an error:

  1. .AddErrorColumn(m => m, "*", width: 20)

Since we put m => m the error column is triggered by whole entity level errors. This way also errors in fields that are not shown in a grid row can be signalled to the user. Error bubbling is useful also in TreeViews/TreeGrids because an error happening in a child entity is signalled also in its father entity, so the user may open the right branch of the tree to find the children entity in error.

Error bubbling is automatically applied to both the errors returned by the server and to client side validation errors.

What if the user want to know exactly which among the fields that are not shown in the grid is in error in order to correct the error? Simple! He just shows the entity in error in a detail view, and thanks to the errors synchronization behavior with detail views provided by the data moving plug-in he will see the error in the detail view!

Another interesting feature is Error Filtering. All Data Moving plug-in controls that have been enhanced with a retrievalManager, have error filtering capabilities. This means, they respond to a “show just entity in error” filtering command that can be issued with a button in a toolbar. This way the user can review all errors by browsing the list of all entities in error.

Everything works properly because the Data Moving engine “remembers” the error state of a field also if the entity the field in error belongs to is removed from the Dom, for instance, because of paging.

In order to minimize the round-trips to the server the Data Moving Plug-in offers the possibility to add entity level validation rules, and whole Core Workspace validation rules directly on the client side.

Below the addition of an entity level validation rule to the programmers updatesManager:

 

  1. TeamBuilding.programmersUpdater.options({ itemErrors: function (x) {
  2.         if (x.CanBeTeamLeader() && (!x.Experience() || x.Experience() < 7))
  3.             return ["A 7 years experience is required to be a Team Leader"];
  4.         else return null;
  5.     }
  6.     });

Validation errors are specified through a function that receives an entity as argument and returns an array of errors. Error dispatching in the adequate place of the UI is done automatically by the Data Moving plug-in engine.

Below the definition of a Core Workspace level validation rule in the whole Workspace updatesManager:

  1. TeamBuilding.ClientModel, "ProposedTeam", TeamBuilding.DestinationModel, "ProposedTeam",
  2. { updatersIndices: [TeamBuilding.programmersUpdater, TeamBuilding.artistsUpdater],
  3.     {
  4.     ......
  5.     ......
  6.     Errors: function (model) {
  7.         if (model.LeaderProgrammer() && model.LeaderArtist()) return null;
  8.         else return ["The team is incomplete"];
  9.     }
  10. });

We can also specify an error callback that is invoked with a data structure containing information on the errors as argument whenever there are errors in the Workspace :

  1. onObjectErrors: function (errorObjects) {
  2.                  alert("Click the error button to show errors that are not visible on the screen");
  3.              }

That’ all for now!

Stay tuned and give a look also to all other Data Moving Plug-in introductory tutorials and videos

                      Francesco

Tags: , , , , , , ,

Mar 18 2013

Single Page Applications 1: Manipulating the Client Side ViewModel

Category: Asp.net | MVC | WebApiFrancesco @ 21:46

Data Moving Plugin Controls

Data Moving Plugin Styling

Data Moving Plugin Forms: Detail Views, Data Filtering UI, and Undo/Redo Stack

Single Page Applications 1: Manipulating the Client Side ViewModel

Single Page Applications 2: Validation Error Handling

Single Page Applications 3: TreeIterator

This is the first of 3 introductory tutorials about the features for handling Single Page Applications offered by The Data Moving Plugin. The Data Moving Plugin is in its RC stage and will be released to the market in about one month.

Firs of all just a little bit theory….then we will move to a practical example. If you want, you may give a look to the video that shows the example working before reading about the theory:

See this Video in High Resolution on the Data Moving Plug-in Site

 

Typically an SPA application allows the user to perform several tasks without leaving its physical Html page. This is result may be achieved by defining several “virtual pages” inside the same physical page. During the whole lifetime of the application just an active virtual page is visible, all other pages are either hidden or completely out of the Dom because they are created dynamically by instantiating client templates. The active page interacts with just a part of the Client Side ViewModel, and only that part is kept in synchrony with the server. 

One can use also different techniques to enable the user to perform several tasks without leaving the l Html physical page; in any case the client ViewModel may be partitioned into subparts that are the smallest “units” that may be sinchronized with the server independently of the remainder of the client side ViewModel. We call such elementary units Workspaces because they are the “data units”  manipulated by the user while he is performing one of the several tasks allowed by the SPA.

A workspace, in turn, is composed of two conceptually different sub-parts: a kind of short living data structure that is used just to carry out the current task and a set of long living data structures that are typically connected with a Database on the server side. Typically, on the client side, we don’t have all long living entities  of a “given type” but just a small window of the whole Entity Set. We call Entity Set Window, the set of all long-living entities of the same type stored in the Client Side ViewModel, and we call Core Workspace the part of the Workspace that remains after removing all Entity Set Windows.

Summing up, the Client side ViewModel is composed of partially overlapping Workspaces, that are in turn composed of a Core WorkSpace and several Entity Set Windows.

In general we can’t assume that all data of the Workspace are someway visible in the user interface. In fact the task being performed currently by the user may be composed of several steps (just think to the steps of a wizard), and substantially just the data “used” in the current step are visible to the user. Accordingly, each Workspace may be further split into partially overlapping UI Units, where each UI Unit is a part of the workspace that is “visible” in the user interface at a given time.

The concept of UI Unit is very important in error handling because, while all UI Units belonging to a Workspace must be submitted simultaneously to the server, only the errors that refer to the current UI Unit can be shown to the user.

The Data Moving Plug-in, offers tools to handle properly Entity Set Windows, Core Workspaces, and for handling properly UI Units during validation error processing:

  1. Retrieval Managers takes care of browsing Entity Sets in the Entity Set Windows, while updatesManagers take care of keeping the Entity Set Windows synchronized with the server by processing updates performed by the users to the Entity Set Windows, and by dispatching the principal key of newly created entities returned by the server.
  2. Whole WorkSpace updatesMangers take care of keeping a whole Workspace synchronized with the server, by automatically issuing commands to the updatesManagers of all Entity Set Windows contained in the Workspace and by taking care “personally” of the Core Workspace.
    The communication protocol between a whole Workspace updatesManager and the server includes the possibility for the server to issue “remote commands” that modify the Core Workspace on the client side. In fact, often, it is not possible for the server, to send a whole “updated” Core Workspace to the client that substitutes completely the old one, because the Core Workspace might have “links” with UI elements and with other Client Side ViewModel data, and a similar substitution would break them.
  3. The Data Moving Plug-in provides a powerful dom element-to-dom element data binding engine that enables the user to trigger “interactions” between dom elements,  and provides also a  Reference Knockout binding that maps UI elements to sub-parts of the Workspace, in such a way that the user “move” such parts of the Workspace by simply moving the UI elements that represent them in an intuitive way. The dom element-to-dom element data binding engine has been already described in a previous tutorial and in a previous video, so in this tutorial we will focus mainly on the Reference binding.
  4. Error Bubbling, Entities in Error Filtering, and other enhancements of the standard Asp.net Mvc validation engine help in associating errors to data that are not immediately visible on the screen. Error handling will be described in the second tutorial about SPA applications:  Single Page Applications 2: Validation Error Handling.

Let understand better how all this works with a simple example(the same shown in the video above).

Suppose we have a list of artists and a list of programmers, that are completely stored in the client side view model, and let suppose we would like to build a team to face a web project made of both artists and programmers. The team will have both a leader programmer and a leader artist, and not all people are entitled to cover the role of leader. Below a screen shot with an indication of the UI elements that represent data of the Core Workspace and data of the Entity Set Windows:

TeamBuilding

In the programmers tab there is another Entity Set Window containing Programmers Entities. Since we said all programmers and all artists are contained in the client ViewModel the Entity Set Windows  contain the whole Entity Sets. Moreover, since both the list of all programmers and the list of all artists are paged, not all all programmers and not artists belong to the current UI Unit; this means we will have difficulties in showing possible errors related to artists and programmers that are not in the current page.

As we can see in the video new people may be added to the Team being built by simply dragging them in the “Members” area. if a new Leader is selected, the old leader is automatically moved back in the original list. People that can cover the role of leader have a yellow border, and the two Leader areas accept only people entitled to cover the Leader role. Moreover, the artists area of the team accepts just artists while the programmers area of the team accepts just programmers.

The whole team building UI logics with the constraints listed above has been obtained without writing a single line of procedural code, but by just declaring reference bindings, Drag Sources, and Drop Targets.

For instance, below the definition of the leader programmer area:

  1.   <div id="leader_programmer"class='leader-container programmers ui-widget-content' data-bind="@bindings.Reference(m => m.ProposedTeam.LeaderProgrammer).Get()">
  2.     @ch._withEmpty(m => m.ProposedTeam.LeaderProgrammer, ExternalContainerType.div, existingTemplate: "ProgrammerTemplate0")
  3. </div>
  4. @Html.DropTarget("#leader_programmer", new List<string> { "LeaderProgrammer" }, rolesDropOptions)

The reference binding maps the div named “leader-programmer” with the property of the Core Workspace ProposedTeam.LeaderProgrammer, while the DropTarget declaration makes it accepts Drag Sources tagged as “LeaderProgrammer”. As a consequence of this two declarations when a UI element representing a programmer entitled to cover the role of leader (ie that has the “LeaderProgrammer” tag) is dragged over this are it is “accepted”, and the data item tied to the dragged UI element with another reference binding, is moved into the knockout observable of the ProposedTeam.LeaderProgrammer property. This in turn triggers the instantiation of the programmerTemplate0 client template because of the _withEmpty instruction that is an enhancement of the knockout with binding.

The ProgrammerTemplate0 templates is the client template automatically built by the grid on the left of the page that lists all programmers. As a consequence the chosen leader programmer is rendered in the “Leader Programmer” area with the same appearance he had in the grid. Each member area works in a similar way:

  1. <div class="members-container programmers ui-widget-content" id ="all_programmers" data-bind="@bindings.Reference(m => m.ProposedTeam.Programmers).Get()">
  2.     @ch._foreachEmpty(m => m.ProposedTeam.Programmers, ExternalContainerType.div, existingTemplate: "ProgrammerTemplate0")
  3. </div>
  4. @Html.DropTarget("#all_programmers", new List<string> { "Programmer" }, rolesDropOptions)

However in this case the ProposedTeam.Programmers property used in the reference binding is an observable array, so the dragged element is pushed into this array. Instead of the _withempty, we have a _foreachEmpty that is an enhancement of knockout foreach binding.

 

To makes everything works properly all programmers must be declared as Drag Sources tagged with “Programmer”. Moreover, all programmers entitled to cover the role of leader must have also the “LeaderProgrammer” tag:

  1. @Html.DragSourceItems(".programmers", ".simple-list-item", new List<string> { "Programmer" }, new DataDragOptions { DestroyOriginal = true, AppendTo = "body" })

The above declaration basically says: “define all elements marked with the class “simple-list-item”  that are descendants of the dom element with class “programmers” as Drag Sources with tag “Programmer”. Now since the whole grid containing all programmers is under a div with class “programmers” and since all rows of this grid have the class “simple-list-item” all programmers are all defined as Drag sources.

The request is extended also to future elements that will be added as descendants of the element with class “programmers“, thus if we insert new elements in the grid they will be automatically declared as Drag Sources.

The “simple-list-item” class is added to each row of the grid as a part of its row definition instructions with:

  1. .ItemRootHtmlAttributes(new Dictionary<string, object> { { "class", "simple-list-item" } })

About the “LeaderProgrammer” tag, it must be added to all data items with the property CanBeTeamLeader set to true. Since this property may change during processing we must add it with a knockout binding attached to the CanBeTeamLeader property:

  1. .KoBindingsGenerator(bb => bb.CSS("LeaderProgrammer", l => l.CanBeTeamLeader)
  2.     .Reference(m => m)
  3.     .Get().ToString())

The KoBindingsGenerator is a method of the fluent interface of the grid row definition. It accepts a function of the type

  1. Func<IBindingsBuilder<U>, string> knockoutBindings

and applies the knockout bindings defined in the body of the function to all rows of the grid, by adding them to the client row template being built by the grid. We use the IBindingsBuilder interface received as argument to build a standard Knockout Css binding that adds the css class “LeaderProgrammer” whenever the property CanBeTeamLeader is true, and a Reference binding that bind each row to its associated data item. The Reference binding enables the “Dragged” programmer to “release” its referred data to the data item referred by the “Drop Traget”.

Since in the options of the DragSourceItems declaration we set DestroyOriginal to true a dropped programmer is removed from the programmers list.

When we put a new Leader Programmer in the Leader Programmer area, the old Leader programmer returns back to the programmers list because we defined the Programmers list as mirroring pool for the programmers entities (this is done in javascript):

  1. ko.mirroring.pool = function (obj) {
  2.     var dis = obj["MainCompetence"];
  3.     dis = ko.utils.unwrapObservable(dis);
  4.     if (dis === "Artist") return TeamBuilding.ClientModel.AllArtsist.Content;
  5.     else if (dis === "Programmer") return TeamBuilding.ClientModel.AllProgrammers.Content;
  6.     else return null;
  7. };

All mirroring pools are defined by assigning a javascript function to the ko.mirroring.pool configuration variable. This function is passed all items that were removed from their places because of a Reference binding based interaction and that were put in no other place, so they “disappeared” from the client side ViewModel. This function is their last chance to find an “home”. This function analyze all properties of each item and possibly find a new “home” for it.

Moving either an artist or a programmer in the detail area assigns a reference to its associated data item to the knockout observable CurrentDetail in the client ViewModel without detaching the data item from its previous place, because in this case the DestroyOriginal option of the drop target is not set to true. This triggers the instantiation of a template that shows the data item in detail mode:

  1. @ch._with0(m => m.CurrentDetail,
  2.     @<text>
  3.         <p>
  4.         <span class='ui-widget-header'>@item.LabelFor(m => m.Name)</span>
  5.         :
  6.         @item.TypedEditDisplayFor(m => m.Name, simpleClick: true)
  7.         @item.ValidationMessageFor(m => m.Name, "*")
  8.         </p>
  9.         <p>
  10.         <span class='ui-widget-header'>@item.LabelFor(m => m.Surname)</span>
  11.         :
  12.         @item.TypedEditDisplayFor(m => m.Surname, simpleClick: true)
  13.         @item.ValidationMessageFor(m => m.Surname, "*")
  14.         </p>
  15.         <p>
  16.         <span class='ui-widget-header'>@item.LabelFor(m => m.EMail)</span>
  17.         :
  18.         @item.TypedEditDisplayFor(m => m.EMail, simpleClick: true)
  19.         @item.ValidationMessageFor(m => m.EMail, "*")
  20.         </p>
  21.         <p>
  22.         <span class='ui-widget-header'>@item.LabelFor(m => m.Address)</span>
  23.         :
  24.         @item.TypedEditDisplayFor(m => m.Address, simpleClick: true)
  25.         @item.ValidationMessageFor(m => m.Address, "*")
  26.         </p>
  27.         <p>
  28.         <span class='ui-widget-header'>@item.LabelFor(m => m.CanBeTeamLeader)</span>
  29.         :
  30.         @item.CheckBoxFor(m => m.CanBeTeamLeader)
  31.         </p>
  32.     </text>
  33. , ExternalContainerType.koComment, afterRender: "mvcct.ko.detailErrors", forceHtmlRefresh: true, isDetail: true)

The _with0 instruction is a different enhancement of the knockout with binding, that accepts an in-line razor helper as client template. Among its arguments there is one named isDetail that we set to true, to inform the Data Moving Plug-in engine that the template is the detail view of a data item. This declaration triggers a synchronization behavior between the original UI of the data item and its detail view.

 

Having finished describing how the user can manipulate the Workspace we can move to see how server-client interaction takes place. The two Entity Set Windows of the Workspace are implemented with two grids. For a detailed description about how to “code” grids you may refer to Data Moving Plugin Controls. Here we point out just that since all data items are already on the client side we must use a local retrievalManager to execute the paging, sorting and filtering queries:

  1. .StartLocalRetrievalManager(m => m.AllProgrammers.Content, true, "TeamBuilding.programmersRM").EndRetrievalManager()

The first argument is the source of all items to be queried(a property of the client side ViewModel), the second argument set to true requires the execution of an initial query as soon as the page is loaded (in order to show some initial data in the grid), and the third argument is where to put the newly created retrievalManager.

The updatesManager of the two grids are both root updatesManager since our items are not children of any one-to-many relation, as in all other examples we have seen in Data Moving Plugin Controls. However, in this case they don’t communicate directly with the server, because we will define a whole WorkSpace updatesManager that will take care of collecting data from the two grids updatesManagers, handling the updates of the Core WorkSpace, communicating with the server, and dispatching the responses of the server to the two grids updatesManagers.

The definition of the programmers updatesManager is:

 

  1. .CreateUpdatesManager<TeamBuildingDestinationViewModel>("TeamBuilding.programmersUpdater", true)
  2.     .BasicInfos(m => m.Id, m => m.ProgrammersChanges, "TeamBuilding.DestinationModel")
  3.     .IsRoot(Url.Action("UpdateTeam"))
  4. .EndUpdatesManager()

It appears more complex of the updates managers we have seen in Data Moving Plugin Controls. The first call to CreateUpdatesManager contains the whole path where to store the updatesManager on the client side instead of the name of the property of the ViewModel where to store it, that’s why the second optional parameter is set to true. Moreover, the method call contains a generic type instantiation, the viewmodel we will use to submit all changes to the server:

  1. public class TeamBuildingDestinationViewModel
  2. {
  3.     public Team ProposedTeam { get; set; }
  4.     public OpenUpdater<Employed, Guid?> ProgrammersChanges { get; set; }
  5.     public OpenUpdater<Employed, Guid?> ArtistsChanges { get; set; }
  6. }

The first property will be filled with the whole Core Workspace, while the other two properties will be filled with the programmers and artists change sets. That’s why the call to BasicInfos has two more parameters after the specification of the principal key: the first parameter is the property of the destination ViewModel where to store the programmers change set, and the third parameter is the property of the whole client ViewModel where to put the destination viewmodel before sending it to the server. The IsRoot method contains a fake url since the destination ViewModel will be posted to the server by the whole Workspace updatesManager.

The whole Workspace updatesManager must be defined in javascript since it is not tied to any specific Data Moving Plugin control:

  1. $('#outerContainer').attr('data-update'),
  2.  TeamBuilding.ClientModel, "ProposedTeam", TeamBuilding.DestinationModel, "ProposedTeam",
  3.  { updatersIndices: [TeamBuilding.programmersUpdater, TeamBuilding.artistsUpdater],
  4.      classifyEntity: function (x) {
  5.          if (x['Id'] && x['MainCompetence'])
  6.              return x.MainCompetence() == "Programmer" ? 0 : 1;
  7.          else
  8.              return null;
  9.      },
  10.      ........

The first argument is the url where to submit the destination ViewModel that is extracted from an Html5 attribute of a dom element. The second argument is the whole client ViewModel and the third argument is the path where to find the Core Workspace within the whole client ViewModel. The fourth argument is the destination ViewModel, and the fifth argument is the path to the place where to store the Core Workspace within the destination ViewModel. Then we have an option argument with several properies. Here we analyze just three of them, since all others are connected to error handling that will be discussed in Single Page Applications 2: Validation Error Handling.

UpdatersIndices is an array containing all updatersManager of the Entity Set Windows of the Workspace; in our case the updatesManagers of the two grids.

classifyEntities is a function that given an entity must return the index in the previous array of its Entity Set Windows updatesManager. This function enables the whole Workspace updatesManager to process adequately all entities it find inside the Core WorkSpace.

That’s enough for everything to work properly! When the user clicks submit the update method of TeamBuilding.updater is invoked, the destination ViewModel is filled, and submitted to the server. When the server send the response the parts of the response destined to the Entity Set Windows updatesManagers will be automatically dispatched to them, and processed automatically. As a consequence, modifications to the the Core Workspace returned as remote commands by the server are applied, keys created for newly inserted entities are dispatched each to its entity, and errors associated to various data elements are dispatched next to the adequate UI elements:

  1. $('#submit').click(function () {
  2.         var form = $(this).closest('form');
  3.         TeamBuilding.ClientModel.CurrentDetail(null);
  4.         if (form.validate().form()) {
  5.             TeamBuilding.updater.update(form);
  6.         }
  7.     });

Let give a look to the action method:

  1. public HttpResponseMessage Post(TeamBuildingDestinationViewModel model)
  2.         {
  3.             if (ModelState.IsValid)
  4.             {
  5.                 try
  6.                 {
  7.                     var builder = ApiResponseBuilder.NewResponseBuilder(model, ModelState, true, "Error in client request");
  8.                     builder.Process(m => m.ArtistsChanges, model.ProposedTeam, m => m.Id);
  9.                     builder.Process(m => m.ProgrammersChanges, model.ProposedTeam, m => m.Id);
  10.                     //business processing here
  11.  
  12.                     var response = builder.GetResponse();
  13.                     return response.Wrap(Request);
  14.                 }
  15.                 catch (Exception ex)
  16.                 {
  17.                     ModelState.AddModelError("", ex.Message);
  18.                     return
  19.                         Request.CreateResponse(System.Net.HttpStatusCode.InternalServerError, new ApiServerErrors(ModelState));
  20.                 }
  21.             }
  22.             return Request.CreateResponse(System.Net.HttpStatusCode.InternalServerError, new ApiServerErrors(ModelState));
  23.         }

This code is very similar to the code we have seen in the action methods that processes the grids updates in Data Moving Plugin Controls: we create an ApiResponseBuilder and then we call the Process method on each of the Entity Set change sets we received in the destination ViewModel. Since our principal key are Guids we dont need to specify a custom key generation function, so the indication of which property is the principal key suffices. However, now the Process methods has 3 arguments, instead of two. We used a different overload! An overload that accepts a Core WorkSpace as second argument. Why we need this further argument? Simple, because we have to process also the changes of the entities that are contained in the Core WorkSpace. In fact, a programmer or artist that we added to the Team might have been modified, or it might be a newly inserted item. The addition of the new argument enables the Process method to include also the entities contained in the Core WorkSpace  in the change sets in their appropriate places if this is necessary.

 

Now suppose we want to modify the client side Core WorkSpace by changing all programmers names with the suffix “Changed” and by adding two more programmers to the team. We need to add adequate remote commands in the response. How to built them? Quite easy! It is enough to create a changes builder object and then to mimic these operations on it:

  1. var changer = builder.NewChangesBuilder(model.ProposedTeam);
  2.  
  3. changer.Down(m => m.Programmers)
  4.     .UpdateModelIenumerable(m => m, m => m.Name, (m, i) => m.Name + "Changed");
  5. changer.UpdateModelField(m => m.LeaderProgrammer, m => m.Name, model.ProposedTeam.LeaderProgrammer.Name + "Changed");
  6. changer.Down(m => m.Programmers)
  7.     .AddToArray(m => m[0],
  8.         new Employed()
  9.         {
  10.             Id = Guid.NewGuid(),
  11.             MainCompetence = "Programmer",
  12.             Name = "John1",
  13.             Surname = "Smith1",
  14.             Address = "New York, USA",
  15.             EMail = "John@dummy.us",
  16.             CanBeTeamLeader = true
  17.         }, 0, true).AddToArray(m => m[0],
  18.             new Employed()
  19.             {
  20.                 Id = Guid.NewGuid(),
  21.                 MainCompetence = "Programmer",
  22.                 Name = "John2",
  23.                 Surname = "Smith2",
  24.                 Address = "New York, USA",
  25.                 EMail = "John@dummy.us"
  26.             }, 0, true);

The first instruction modifies the names of the programmers that are simple members of the team(actually it just creates the remote command to do this). We go down the Programmers properties of the Core Workspace and then call the UpdateModelIEnumerable that applies a modifications to all elements of an IEnumerable. The first argument specify the IEnumerable to be modified; since we already moved into the IEnumerable it is just m => m. The second argument specifies the property of each element that must me modified and the third argument specifies how to modify it.

The second instruction modifies the LeaderProgrammer name.  It is self-explanatory.

Finally, the third instruction adds two more programmers. We move down the Programmers property, and then we call AddToArray twice. The first argument of each call specifies the place in the javascript array where to place the newly added element: in our case we place it at index 0….but wait …wait wait, since the last argument of the call is set to true the enumeration starts from the bottom, so we are just queuing the new elements at the bottom of the array.

Now in order to include all “remote commands” in the response we must substitute:

  1. var response = builder.GetResponse();

with:

  1. var response = builder.GetResponse(changer.Get());

However, we have a problem, the two programmers that we added to the team might be already contained in the programmers list so we might have an entity duplication in the client side View Model. Luckily, the Data Moving Plug-in offers tools to enforce  uniqueness.we may trigger the processing that enforce uniqueness of entities in onUpdateComplete callback of the whole WorkSpace updatesManager (defined in its options):

  1. onUpdateComplete: function (e, result, status) {
  2.     if (!e.success) return;
  3.     var hash = {};
  4.     mvcct.updatesManager.utils.entitiesInWorkSpace(TeamBuilding.ClientModel.ProposedTeam, hash);
  5.     TeamBuilding.programmersUpdater.filterObservable(hash);
  6.     TeamBuilding.artistsUpdater.filterObservable(hash);
  7. },

The mvcct.updatesManager.utils.entitiesInWorkSpace method extracts all entities contained in the core workspace, and index them into an hash table. After that, each Entity Set updatesManager ensures they are not contained in the Entity Set Window it takes care of. The task is carried out efficiently because of the indexing performed by mvcct.updatesManager.utils.entitiesInWorkSpace .

That’ all for now!

Stay tuned and give a look also to all other Data Moving Plug-in introductory tutorials and videos

                      Francesco

Tags: , , , , , ,

Mar 15 2013

Data Moving Plugin Controls

Category: Asp.net | MVC | WebApiFrancesco @ 00:09

Data Moving Plugin Controls

Data Moving Plugin Styling

Data Moving Plugin Forms: Detail Views, Data Filtering UI, and Undo/Redo Stack

Single Page Applications 1: Manipulating the Client Side ViewModel

Single Page Applications 2: Validation Error Handling

Single Page Applications 3: TreeIterator

The Data Moving Plug-in is in its RC stage and will be released to the market within about one month. This is the first of 6 introductory tutorials with associated videos about it.

All Controls provided in the Data Moving Plug-in are compatible with both mouse based devices and with touch devices. Moreover all controls are accessible, and the user can interact with them with the only support of the keyboard.

From a conceptual point of view all controls can be classified into two big categories: Client Controls and Server Controls. Client Controls are bound to client side javascript data and create their Html dynamically on the client side, while the Html of Server Controls is rendered on the server side using data contained in a server side ViewModel.

The main advantages of server controls is that their ”static” Html is visible to the search engines, and that they require less “job” on the client side so they are efficiently rendered also by low performance browsers (such as the browsers of low quality mobile devices). On the other side client controls offer more flexibility, and a better interaction with all other html elements of the page. 

The Data Moving Plug-in contains both type of controls, in order to fit better the developers needs. Typically, server side controls communicate with the server through form submits, or through ajax posts that return new Html. Below a grid that filters, pages,sorts and updates data through form submits:

ServerGrid

Item editing may be performed either on line (on the rows themselves) or through a detail window that appears when the user clicks the edit button that is on the left of each row:

EditWindow

A similar windows is used also to filter data.

All these features come at 0 cost since they require no coding. We just need to specify the services required through a fluent interface:

  1. .DeclareQueryResolver(Html,  m => m.PreviousQuery, enablePrevPage: true,  enablePageSize:true)
  2. .CreateDynamicSubmitRetrievalManager("GridExample.QueryModel.RM", actionUrl: Url.Action("IndexQuery", "GridsDemo"),  newPrefix: "")
  3. .DetailFilterBuilder(out detailBuilder)

DeclareQueryResolver specifies the part of the server side  ViewModel where to store all query information (sorting, filtering, etc). The Data Moving Plugin offers the QueryViewModel<T> pre-defined class for this job but the user may choose to configure a custom class. We need just to add this class to our ViewModel, and the Data Moving Plug-in takes care of everything else. The services required (filtering, paging, sorting) are specified with optional arguments of the call: as default all services are enabled. The third argument of DeclareQueryResolver enables the user choice of the page size, while the second argument requires that the paging engine “remembers” the previous page, so that if a page change fails it can return to the previous page. Once we have enabled paging with DeclareQueryResolver, it is enough to add a pager column to a toolbar to have the a working paging service:

  1. .AddPagerColumn("FullCompletePager")

The name passed as argument to the pager column is a reference to a pager “prototype” we defined in a configuration class.

In fact, in order to simplify controls coding and to allow reusability of code, the developer has the option to store controls “options” in a configuration class by defining both controls “prototypes”, and row “prototypes”. Prototypes, may contain all control or row settings that are not specific for a particular data item.

Since, we required user choice of the page size, the pager will automatically show also a textbox to enter the page size.

The CreateDynamicSubmitRetrievalManager methods gives information on how to send queries to the server. The first parameter is a javascript property where to store the RetrievalManager javascript object that will take care of managing all queries-related communication with the server(this is useful if we would like to customize its behavior on the client side). The second parameter is the url of the action method that processes the query, and finally the last argument specifies a possible prefix to add to the quey ViewModel.  This parameter is useful if the model accepted by the action method is not just a QueryViewModel<T>, but  a more complex model containing QueryViewModel<T>  in one of its properties. In our case (and in most of the cases) the prefix must be empty.

The DetailFilterBuilder method provides an object we may use to render the edit/detail window. For more information about edit/detail windows please refer to Data Moving Plugin Forms: Detail Views, Data Filtering UI, and Undo/Redo Stack.

On the server side the query processing is straightforward:

  1. public ActionResult IndexQuery(QueryViewModel<HumanResource> query) //read-edit simple server grid
  2. {
  3.     prepareData();
  4.     IEnumerable<HumanResource> res = fakeDB.Get();
  5.     if (query != null)
  6.     {
  7.         res = query.ApplyToIEnumerable(res, true, true, pageSize);
  8.     }
  9.     var model = new TrackedGridDemoViewModel { Staff = res.Select(m => new Tracker<HumanResource> { Value = m, OldValue = m }), PreviousQuery = query, ViewSelector = null };
  10.     return View(selectViewTracked(model.ViewSelector), model);
  11. }

PrepareData just retrieve a fake Db (implemented with a dictionary)  stored in the Session. The query received from the client is applied to the fake Table with a single call to ApplyToEnumerable. In the case of an actual DB we must use the method ApplyToQueryable, instead.  Then all data are placed in the page ViewModel.

As you can see all items of the list obtained as result of the execution of the query are enclosed within a Tracker Object. The Tracker object enables Changes Tracking on the grid. There are two kind of server grids: the first one accepts directly a list of Tracker<T> objects and takes care automatically of changes tracking, the other one needs and adapter that adds the needed changes tracking capabilities. Below how to use the adapter:

  1. var h = Html.TrackedListRendering(m => m.Staff);
  2. var dBuilder = h.SimpleGrid(m => m.Values, false, true)
  3. .EnableAlternateStyle()
  4. ...........

As you can see the call to the adapter TrackedListRendering returns an Html helper that we can use to render the grid.

The user can add, delete and modify rows. When he hits the submit button, the whole form the Grid is enclosed in is submitted to the server. Below the Action Method that processes this submit:

  1. //Action methods to process item changes
  2. [HttpPost]
  3. public ActionResult TrackedIndex(TrackedGridDemoViewModel model)
  4. {
  5.     prepareData();
  6.     
  7.     if (ModelState.IsValid)
  8.     {
  9.         ModelState.Clear();
  10.         if (model != null)
  11.         {
  12.             IList<HumanResource> inserts, deletes, modified;
  13.             model.Staff.GetChanges(out inserts, out deletes, out modified, m => { m.Id = Guid.NewGuid(); });
  14.             fakeDB.Insert(inserts); fakeDB.Delete(deletes); fakeDB.Modify(modified);
  15.             QueryViewModel<HumanResource> startQuery = model.PreviousQuery != null ? model.PreviousQuery :  new QueryViewModel<HumanResource>().AddSortCondition(m => m.Surname, OrderType.Ascending);
  16.             model = new TrackedGridDemoViewModel { ViewSelector = model.ViewSelector, Staff = startQuery.ApplyToIEnumerable(fakeDB.Get(), true, true, pageSize).Select(m => new Tracker<HumanResource> { Value = m, OldValue = m }), PreviousQuery = startQuery };
  17.         }
  18.  
  19.     }
  20.     else
  21.     {
  22.         if (model != null && model.PreviousQuery != null)
  23.         {
  24.             model.PreviousQuery.Page = model.PreviousQuery.PreviousPage;
  25.             model.PreviousQuery.SortExpression = model.PreviousQuery.PreviousSortExpression;
  26.         }
  27.     }
  28.     return View(selectViewTracked(model.ViewSelector), model);
  29. }

 

Since we enclosed our items within Tracker objects we are entitled to call the GetChanges method that computes all changes in the IEnumerable items and returns the three lists of all inserted, deleted and modified items. The fourth argument of the GetChanges method, if provided, must be am Action that is applied to all inserted elements. Typically it is used to add a principal key to all Inserted elements (when this is possible before accessing the database).

 

In case we use a Client Side Grid the first step is to move a part of the Server Side ViewModel to the client side, and to get an Html helper that has the capabilities to render client side controls. Both tasks are accomplished with a simple call to the SendToClient method:

  1. @{var h = Html.SendToClient(m => m.ClientModel, "GridDemo.ViewModel");}

The second argument just says where to store the Client Side ViewModel.

Now we may use h to specify all options of our grid and to render it:

  1. var dBuilder = h.SimpleGrid(m => m.StaffToShow, true, true, hasRowDisplayAndRowEdit: true).......

Since our client side grid uses OData for the queries the method calls that enable the query engine are a little bit different:

  1. .CreateStandardQueryResolver(Model.PreviousQuery, enablePrevPage: true, enablePageSize: true)
  2. .StartODataRetrievalManager(false, "GridExample.QueryModel.RM", (uint)Model.PreviousQuery.PageSize, actionUrl: Url.HttpRouteUrl("DefaultApi", new { httproute = "", controller = "GridsDemoApi"}))

In this case we call the CreateStandardQueryReoslver method instead of DeclareQueryReolver because the server side models doesn’t need to contain any object to store query information, since all query handling is done on the client side. Accordingly an instance of QueryViewModel<T> is just created and inserted in the Client Side ViewModel in a way that is completely transparent to the developer. However, in our case we add an instance of QueryViewModel<T> also to the server side ViewModel: this instance of QueryViewModel<T> doesn’t take part to any query processing but we use it just to initialize the client side query by passing it as first parameter to the CreateStandardQueryReoslver.

StartODataRetrievalManager specifies the use of a RetrievalManager that is able to communicate with OData points. This javascript RetrievalManger object is stored in the GridExample.QueryModel.RM property. The first argument of StartODataRetrievalManager  set to false says we dont want to issue an initial query immediately after the page is rendered because the initial data have already been passed in the initial Client Side ViewModel. The third argument just says the initial page size to use for paging: this value will probably change during the grid operation since we enabled user choice of the page size. Finally, the last argument is the url of the WebApi controller that processes the queries.

Client grids are able to send items changes to the server with a simple form submit in exactly the same way a server grid would do, but the preferred way to communicate with the server is by sending data in json format with an ajax call. This job is done by the updatesManager javascript class that takes care of computing changes on the client side and to send Inserted, updated, and deleted items to the server in json format (just the keys of the deleted elements are sent to the server).

No javascript coding is required to use an updatesManager class; we need just to declare it with a fluent interface:

  1. .CreateUpdatesManager("UM").BasicInfos(m => m.Id).IsRoot(Url.HttpRouteUrl("DefaultApi", new { httproute = "", controller = "GridsDemoApi" })).EndUpdatesManager()

 

UM is the name of the property of the Client Side ViewModel where to store the newly created updatesManager class, m => m.Id specifies the principal key of the items. Finally, the IsRoot call specifies that this is a root updatesManager that takes care of “interfacing” directly the controller. In fact, there might be also children updatesManagers that takes care of the children of a one-to-many relation, and that delegate the communication with the server to the updatesManager of the father items. The only argument of IsRoot is the url of the action method that processes the updates. Children updatesManagers are discusses in this video.

The controller receives a standard OpenUpdater<M,K> model where M is the type of the items and K is the type of their principal key. In case the page contains several grids and/or several type of entities the controller may receive a complex model containing several OpenUpdater<M,K> inside different properties and possibly also other data the client needs to send to the server. For more information on complex updates please refer to Single Page Applications 1: Manipulating the Client Side ViewModel.

Processing of the OpenUpdater<M,K> is done quite automatically by the ApiResponseBuilder class that takes care of building a response in the format accepted as response by the updatesManger. This response might contain either validation errors or the keys of the Inserted elements computed by the server. In case of a complex model with several OpenUpdater<M,K> the ApiResponseBuilder is able to build a complex response whose parts will be dispatched adequately once the response reaches the client side. The way ApiResponseBuilder handles complex models is detailed in Single Page Applications 1: Manipulating the Client Side ViewModel.

In our simple case:

  1. public HttpResponseMessage Post(OpenUpdater<HumanResource, Guid?> model)
  2.         {
  3.             prepareData();
  4.             //ModelState.AddModelError("", "test error");
  5.             if (ModelState.IsValid)
  6.             {
  7.                 try
  8.                 {
  9.                     var builder = ApiResponseBuilder.NewResponseBuilder(model, ModelState, true, "Error in client request");
  10.                     builder.Process(m => m, m => m.Id);
  11.                     //call to business layer
  12.  
  13.                     fakeDB.Insert(model.Inserted); fakeDB.Delete(model.Deleted); fakeDB.Modify(model.Modified);
  14.                     //
  15.                     var response = builder.GetResponse();
  16.                     return response.Wrap(this.Request);
  17.                 }
  18.                 catch (Exception ex)
  19.                 {
  20.                     ModelState.AddModelError("", ex.Message);
  21.                     return
  22.                         Request.CreateResponse(System.Net.HttpStatusCode.InternalServerError,new ApiServerErrors(ModelState));
  23.                 }
  24.             }
  25.             else return
  26.                 Request.CreateResponse(System.Net.HttpStatusCode.InternalServerError, new ApiServerErrors(ModelState));
  27.         }

In case there is no error we create an ApiResponseBuilder object with a call to NewResponseBuilder. We pass to this object both, the whole model, the ModelState and a default error message to be used in case of hill formed requests. The third argument set to true, require to throw an exception in case of hill formed requests.

The Process method performs all needed key processing for the newly inserted elements. In our case the processing is simple since we have no one-to-many relations, so we need just to provide principal keys to the newly inserted elements. The first argument selects what OpenUpdater<M,K> to process (this argument is needed to handle also complex models with several OpenUpdater<M,K>); in our case it is trivial: m => m. The second argument selects the principal key of the items contained in the selected OpenUpdater<M,K>. A function that receives as input an item and returns a newly computed principal key for it may be passed as third optional argument. Since we have not provided this function, the default Guid key generator is used.

In case of errors we create an ApiServerErrors object that extracts automatically all errors from the ModelState and put them into an Api response with the Internal Server Error header.

In case the receiving controller is not a WebApi controller but a standard Mvc controller we have to substitute the ApiResponseBuilder class with the ResponseBuilder class and the ApiServerErrors class with the ServerErrors class. Moreover the response must be returned directly with return Json(response), and the errors with return Json(new ServerErrors(ModelState)).

 

The way to style and decide the appearance of both server and client grids is substantially the same. We may specify options with a fluent interface, add toolbars, and  define data rows options.

Both toolbars and data rows are composed of columns that are arranged according to a row template. The developer may choose between three pre-defined row templates:

  1. A <table> based template that may be used in case of tabular data.
  2. A <div style=”display: table”…based template if we need a table like appearance but the data are not “tabular”
  3. A div/float based template.

Moreover, the developer can furnish also its own custom row template, that either arranges the pre-existing column definitions or renders directly the item without taking care of column definitions. There are different types of columns:

  1. Standard columns. Their default template may be controlled with a fluent interface. They are able to render properly any .Net data type both in edit and in display mode. We may choose to use the Mvc Display and Edit templates defined for the given types, or Display only, and TypedTextBoxes based templates that are automatically optimized for each data type. It is also possible to specify the use of the new Html5 inputs; the selection of the input type is done according to the column data type and to a possible DataType attribute that may decorate the property associated to the column.
  2. Image columns. They extracts both the src and the alt of the image from the item data;
  3. Link columns capable of extracting both the href an the link text from the item data.
  4. Text Columns, to render constant text or constant Html.
  5. Button Columns, to render single buttons or buttons organized in bars.
  6. Pager Columns, to display a pager.
  7. RowCount columns, to count rows
  8. Error Column, to display errors associated to the whole row.

 

All columns have standard Header, Footer, edit, Display, Edit Detail, Display Detail,  and Filter templates that can be customized with a fluent interface, but for each of them the developer may provide a custom template.

Below the definition of a toolbar that contains a a button that opens the filter data dialog, and a pager:

  1. .StartToolbar(false)
  2.         .RowContainerLevel(ItemContainerLevel.Row)
  3.         .RowHeight("3em", true)
  4.         .AddButtonToolbar(ShowButtonIn.Both, CommandButtonType.FilterWindow).ColumnWidth(40).EndButtons()
  5.         .AddPagerColumn("FullCompletePager")
  6.         .EndToolBar()

 

Below the definition of a data row:

  1. .AddRowType(true, true)
  2.             .DeclareQueryResolver(Html,  m => m.PreviousQuery, enablePrevPage: true,  enablePageSize:true)
  3.             .CreateDynamicSubmitRetrievalManager("GridExample.QueryModel.RM", actionUrl: Url.Action("IndexQuery", "GridsDemo"),  newPrefix: "")
  4.             .DeclareDisplayStore()
  5.             .DetailFilterBuilder(out detailBuilder)
  6.             .RowContainerLevel(ItemContainerLevel.Row)
  7.             .DeclareInvisibleInnerRowContainer()
  8.             .HtmlTitle(ShowTitleIn.Display | ShowTitleIn.Edit)
  9.             .RowHeight("3em", true)
  10.             .AddRowCountColumn(false, width: 4, widthIsPercentage: true)
  11.             .AddButtonColumn(ShowButtonIn.Both, CommandButtonType.EditWindow, "GridExample.selectItem GridExample.unselectItem").ColumnWidth(4, true).HorizontalAlign(MVCControlsToolkit.Controls.Core.HAlign.center).EndButtons()
  12.             .StartColumn(t => t.Name, width: 46, widthIsPercentage: true).Queries(true, true).HorizontalAlign(MVCControlsToolkit.Controls.Core.HAlign.center).EndColumn()
  13.             .StartColumn(t => t.Surname, width: 46, widthIsPercentage: true).Queries(true, true).HorizontalAlign(MVCControlsToolkit.Controls.Core.HAlign.center).EndColumn()
  14.             .AddColumn(t => t.Address, true)
  15.             .AddImageColumn(t => t.AvatarAlt, t => t.AvatarUrl, new { style = "width: 100px; height: 100px;" }, true)
  16.             .StartColumn(t => t.Id).DeclareHidden().EndColumn()
  17.         .EndRowType();

 

It contains the query related methods we already discussed before, the DeclareDisplayStore() method call that require that the rows will work just in display mode, but that they store fields values in hidden fields, so that the row content can be edited with the help of an edit window.

The HtmlTitle() method requires to add an Html title attribute to all columns with the same content of the column field (useful if the content of the field is not fully visible, but it appears “dotted”). There is a RowCountColumn, and a ButtonColumn that opens an edit row dialog.

Then, we have the Name and Surname field columns. Both of them make the call Queries(true, true), that enables both sorting and filtering on them.

Interesting also the Image column for the avatar. It extracts both the src, and the alt from the item. The last argument set to true specifies that the image column must appear just in the detail window.

Finally, The column for the principal key is declared hidden because we don’t want to show the Id, but just to store it into an hidden field.

The Data Moving Plug-in includes 4 different types of grids(two are server side controls and the other two are client side controls), a TreeGrid/TreeView, and a menu control. The TreeGrid/TreeView working is shown in this video. The menu control may be displayed both horizontally and vertically; it works both with mouse hover or with mouse click (or touch in case of touch devices). Moreover, also all menu items use the Data Moving Plug-in row templates engine we described before for grids.

The Data Moving Plugin contains also a powerful Form Control, with undo/redo capabilities, and a DualSelect to select items from a pre-existing list, that are able to work both as server side controls and as client side controls. Both of them are described in Data Moving Plugin Forms: Detail Views, Data Filtering UI, and Undo/Redo Stack and in its associated video.

Included in the plug-in also powerful knockout bindings for jqPlot and tinyMce. Moreover, tinyMce has been enhanced with a “documents template engine” that give us the possibility to define document templates containing “variables” that can be instantiated either with the content of other input fields or with the content of javascript data structures. This video shows both the enhancements provided to jQplot, and tinyMvce and the documents template engine.

Finally, the developer has access also to all Mvc Controls Toolkit controls, such as TypedTextBox, TypedEditDisplay, DateTimeInput, etc. They can me mixed with all Data Moving Plug-in controls and they can be used also in all template definitions.

Below a video that shows a review of all Data Moving Plug-in Controls:

That’ all for now!

Stay tuned and give a look also to all other Data Moving Plugin introductory tutorials and videos

                      Francesco

Tags: , , , , , ,

Nov 15 2011

Mvc Controls Toolkit Datagrid Updated Tutorial

Category: MVC | Entity Framework | Asp.netFrancesco @ 23:42

 

This post is an updated  tutorial on how to use the Update/Delete/Insert Templated datagrid of the MVC Controls Toolkit. It contains information already published in previous tutorials updated to the new versions of the MVC Controls Toolkit. The full code used in this tutorial can be found in the Mvc3 Razor folder of the zipped file BasicTutorialsCode  here

The commercial version of the toolkit contains datagrids with several more options, and that may be configured and styled more quickly with a fluent interface.

Our Data model is simply a Todo List with four fields: Name(varchar), Description(varchar), DueDate(date), and the principal key id of type identity. First, we define the Database, and a table named ToDo with the previous four fields.

Next, we create an Entity Framework(EF) model based on this database. We then create a MetaClass to handle the constraints on our ToDo items. Let say that the DueDate can range from 3  months before today to 6 months after today. Since today is not an absolute value such a constraint cannot be interpreted as a Data Layer constraint, therefore it sholdn’t be put with the other data constraints of the data layer. We will take care of it in a few minutes ! First lets take care of the other simpler constraints, and add to our project a new file named Todo.cs just under the Models folder. What we put in this file is quite standard:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.ComponentModel.DataAnnotations;
using MVCControlsToolkit.DataAnnotations;

namespace Mvc_Examples.Models
{
    [MetadataType(typeof(MetaToDo))]
    public partial class ToDo
    {

    }
    public class MetaToDo
    {
        
        [Required, CanSort, Display(Name="Name")]
        public object Name { get; set; }
        [Required, Display(ShortName = "Description")]
        public object Description { get; set; }
        [CanSort, Display(ShortName = "Due Date"), Format(DataFormatString="{0:D}")]
        public object DueDate { get; set; }
    }
}

The Display attribute is  a standard DataAnnotation attribute and it just declares the string to be used in the labels for our properties. The CanSort attribute comes from the MVC Controls Toolkit and it declares that the field can be used in sorting operations. We will come back on this later on, when we will speak about the sorting helpers of the MVC Controls Toolkit.

Now let go to the View Model! What do we need to put into our View Model? For sure the ToDo items extracted from the database. However, we would like the items to be pageable, so we have to insert at least a Page property containing the current page. A single Page int is enough for the MVC Controls Toolkit pager to work; for a better paging experience you can supply the total number of pages.

Now…the user may edit some fields and then he may change page. What happens if there are validation errors in his editing? A good option is to go back to the previous page and force him to correct the errors. Therefore, we have to remember what page we came from. Thus we need also a previous page property in our View Model. Luckily we don’t need to put it in a hidden field because our pager already offers this type of service when a “previous page” property is available.

Summing Up, our View Model has the following properties: CurrPage, PrevPage, the optional TotalPages, plus a ToDoList property containing all ToDo items.

Now we have to decide how to handle the strange constraint on the DueDate. One way to handle it is to define a View Model version of the ToDo class where we can apply this Presentation Layer specific constraint. We can use the Mvc Controls Toolkit DateRangeAttribute, that offers the ability to define constraints based on expressions containing “Today” or “Now”:

[MetadataType(typeof(MetaToDo))]
    public partial class ToDoView
    {
        public int? id { get; set; }

        public string Name { get; set; }

        public string Description { set; get; }

        [DateRange(SMinimum = "Today-3M", SMaximum = "Today+6M")]
        public DateTime DueDate {set;get;}

       

    }

Note that we have used the same MetaData class of the original ToDo class. This is important in order to avoid code duplications! As a general rule when we build a View Model either we use  the original data classes, or for  each of the original data classes we define a ViewModel version of it and use it as a child of the page ViewModel. This way, we can use the same metaclasses. You should avoid putting fields from more than one data class into a single View Model Class. An exception to this rule is if data are someway aggregated and transformed into other properties. It is preferred to keep a one to one correspondence between the original data classes and the classes used in the View Model; this way we increase modularity and reuse the metadata classes of the original data classes(duplicating code often causes a lot of problems…).

Our next step is the design of the data access procedures. A best practices is to not insert them into the controller methods, because they might be useful to more than one controller, and because it is always better to keep the data layer separate from the controller layer. We create them as static methods of our View Model. This approach is the standard for accessing ToDo items (we will use it each time paged ToDo items are needed). This choice is acceptable for this simple application, but in different situations we might have introduced a new Repository class.

Summing up our View Model contains:

public int TotalPages { get; set; }
public int CurrPage { get; set; }
public int PrevPage { get; set; }
public List<Tracker<ToDoView>> ToDoList {get; set;}

Plus two static methods: GetToDoPage and UpdatePage, for retrieving one page of data, and for passing to the database the updates made by the user to one page of data.

In order to help passing changes to the database the MVC Controls Toolkit provides the class Tacker<T> that is a wrapper put around a data item. It maintains two versions of the data item, the original version and the one with the changes applied by the user. It also has a Boolean value Changed to signal that the two versions are different.

Comparison between the two versions yields the operation to be done on the database:

  • Old version null and new version non-null: Insert
  • Old version non-null and new version null: Delete
  • Both versions non-null: we have an update

Lets analyze the GetToDoPage method:

public static List<Tracker<ToDoView>> GetToDoPage(int pageDim, out int totalPages, ref List<KeyValuePair<LambdaExpression, OrderType>> order, int page = 1)
{
    List<Tracker<ToDoView>> result;
    if (order == null)
    {
        order = new List<KeyValuePair<LambdaExpression, OrderType>>();
       
    }
    if (order.Count == 0)//paging require ordering! Therefore we always need to add a default oredering
    {
        Expression<Func<ToDoView, DateTime>> defaultOrder = m => m.DueDate;

        order.Add(new KeyValuePair<LambdaExpression, OrderType>(defaultOrder, OrderType.Descending));
    }
    using (SiteDbEntities context = new SiteDbEntities())
    {
        int rowCount = context.ToDo.Count();
        
        if (rowCount == 0)
        {
            totalPages=0;
            return new List<Tracker<ToDoView>>();
        }
        totalPages = rowCount / pageDim;
        if (rowCount % pageDim > 0) totalPages++;
        if (page > totalPages) page = totalPages;
        if (page < 1) page = 1;
        int toSkip = (page-1) * pageDim;

        
            result = context.ToDo.Select(item =>
                new ToDoView() { Name = item.Name, Description = item.Description, DueDate = item.DueDate, id = item.id }).ApplyOrder(order).Select(viewItem =>
                new Tracker<ToDoView>
                        {
                            Value = viewItem,
                            OldValue = viewItem,
                            Changed = false
                        }).Skip(toSkip).Take(pageDim).ToList();
        
    }
    return result;
}

The return is of type List<Tracker<ToDoView>> since we have put our wrapper around each data item. We create a context, with the using keyword to guarantee it will be disposed at the end of the operation (because it contains a connection to the database that is not a managed object).

As a first operation we count the total rows, then we do some mathematics to compute the pages: the remainder operation % is needed to take into account partially filled pages. In order to reach the request page we use the Skip and Take methods. In the select construct we create our wrapper and fill it with two copies of the same data item; one for the previous and one for the updated version of the data item. Note we transfer data from the ToDo object into a fresh ToDoView object.

The order parameter contains field sorting information that are passed as a list of couples. Each couple contains a lambda expression that specifies a field, and an OrderType value that specifies the kind of sorting (ascending or descending). The sorting information is passed to the controller by the EnableSortingFor helper (discussed later in in this post). The MVC Controls Toolkit defines extension methods to apply the sorting information to any IEnumerable or IQueryable. You only need to include the namespace: MVCControlsToolkit.Linq and any IEnumerable or IQueryable will be enriched with the method ApplyOrder that accepts the above list as argument. If an ordering is already defined on either the IEnumerable or the IQueryable the new sorting will be chained Lexicographically with it.

The full code contains also the possibility for filter data. The interested reader may refer to my new tutorial on Data Filtering: Advanced Data Filtering Techniques in the Mvc Controls Toolkit and to my previous tutorial: Data Filtering in the New Mvc 3 Version of The Mvc Controls Toolkit

The UpdatePage method is a little bit more complex, but quite easy, too:

public static void UpdatePage(List<Tracker<ToDoView>> items)
{
    if (items == null) return;
    using (SiteDbEntities context = new SiteDbEntities())
    {
        bool aChange = false;
        foreach (Tracker<ToDoView> item in items)
        {
            if (item.Changed)
            {
                if (item.OldValue == null) //insertion
                {
                    if (item.Value != null)
                    {
                        ToDo curr=new ToDo()
                                 { Name = item.Value.Name, Description = item.Value.Description, DueDate = item.Value.DueDate };
                        aChange = true;
                        context.ToDo.AddObject(curr);
                    }
                }
                else if (item.Value == null) //deletion
                {
                    ToDo curr=new ToDo() { Name = item.OldValue.Name, Description = item.OldValue.Description, DueDate = item.OldValue.DueDate, id=item.OldValue.id.Value };
                    context.ToDo.Attach(curr);
                    context.ObjectStateManager.ChangeObjectState(curr, System.Data.EntityState.Deleted);
                    aChange = true;
                }
                else//update
                {
                    ToDo curr = new ToDo() { Name = item.Value.Name, Description = item.Value.Description, DueDate = item.Value.DueDate, id=item.Value.id.Value };
                    context.ToDo.Attach(curr);
                    context.ObjectStateManager.ChangeObjectState(curr, System.Data.EntityState.Modified);
                    aChange = true;
                }
            }
        }
        if (aChange)
        {
            try
            {
                context.SaveChanges();
                items.ForEach((item) => { item.Confirm(); });//confirm changes have been passed
            }
            catch
            {
            }
        }
    }
}

We have a loop on all modified items where we verify if the item has changed, and if it has changed we analyze what operation needs to be passed to the database as previously.explained. Note the use of the ObjectStateManger to set the correct state of the various objects in the different cases. Insertion is the only case that doesn’t require manually setting the state of the object.

If at least a data item has changed we do a SubmitChanges() that passes all changes in a single transaction to the database. If no exception occurs we call the Confirm() method of the Tracker<T> wrapper that sets the old version of the data item  equal to the new version of it since all changes have been persisted in the database. In case of exceptions an error message should be returned to the controller that instructs the user to make corrections and retry the post. We have not handled this to keep the sample simple.

Now we can go to the controller that has just two Action methods, one for handling the initial HttpGet and the second for handling the subsequent HttpPost:

public const int PageDim=5;//in actual application this should be put in a config file
public ActionResult Index()
{
    int totalPages;
    List<KeyValuePair<LambdaExpression, OrderType>> order = null;
    ToDoViewModel result = new ToDoViewModel()
        {
            ToDoList = ToDoViewModel.GetToDoPage(PageDim, out totalPages, ref order),
            TotalPages = totalPages,
            CurrPage=1,
            PrevPage=1,
            ToDoOrder=order
        };
    return View(result);
}

[HttpPost, System.Web.Mvc.OutputCache(NoStore = true, Duration = 0, VaryByParam = "*")]
public ActionResult Index(ToDoViewModel model)
{
    if (!ModelState.IsValid)
    {
        
        model.CurrPage=model.PrevPage; //cancel possible page change and force correcting errors
        return View(model);
    }
    else
    {
        ModelState.Clear();
        ToDoViewModel.UpdatePage(model.ToDoList);
        int totalPages;
        if (model.CurrPage < 1) model.CurrPage = 1;
        List<KeyValuePair<LambdaExpression, OrderType>> order = model.ToDoOrder;
        ToDoViewModel result = new ToDoViewModel()
        {
            ToDoList = ToDoViewModel.GetToDoPage(PageDim, out totalPages, ref order, model.CurrPage, model.ToDoFilter),
            TotalPages = totalPages,
            CurrPage = Math.Min(model.CurrPage, totalPages),
            PrevPage = Math.Min(model.CurrPage, totalPages),
            ToDoFilter = model.ToDoFilter,
            ToDoOrder=order
        };
        return View(result);
    }
}

The first method just displays the first page and it is quite trivial. The second method handles validation errors. If there are validation errors it cancels the page change by resetting the current page to the previous page, and then returns the same View Model it received in order to let the user corrects the errors. If everything is ok it passes the changes to the database, and retrieves the new page requested by the user. That’s all!

We finally arrived to the datagrid. In order to have the datagrid working we need to prepare 4 templates:

  1. displayTemplate: it displays a row of data when the grid is in display mode
  2. editTemplate: it displays a row of data when the grid is in edit mode
  3. addDisplayTemplate: it defines the look of the insert new row component, normally it just displays an insert button.
  4. gridTemplate: it displays the general container where all data items will be inserted. In our case it is just a table.

As discussed in the documentation about templates, Templates can be passed both as: Partial Views names, Razor Templates, Razor in-line templates, or Lambda Expressions. Here, we will use Razor in-line templates. The reader interested in Partial Views may refer to my previous post: Defining Mvc Controls 2: Using the DataGrid.

Razor in-line templates can be passed directly in the DatagridFor call as arguments. They receive an HtmlHelper<ToDoView> object as the value of a standard parameter called item. We can use this item  variable in exactly the same way we use the Html variable in a standard View.

Lets see in detail each template.

displayTemplate
@<text>         
    <td class="ToDo">
        @item.ValidationMessageFor(m => m.Name, "*")
        @item.DisplayField(m => m.Name)
    </td>
    <td class="editor-field">
        @item.ValidationMessageFor(m => m.DueDate, "*")
        @item.DisplayField(m => m.DueDate)
    </td>
    <td class="ToDo">
        @item.ValidationMessageFor(m => m.Description, "*")
        @item.DisplayField(m => m.Description)
    </td>
    <td class="ToDoTool">
        @item.DetailLink(Ajax, "Edit Details", DetailType.Edit, "ToDoSubTasks", "Home",
            new {
                id = item.ViewData.Model.id},
                                null)
        @item.ImgDataButton(DataButtonType.Edit, "../../Content/edit.jpg", null)
    
    </td>
    <td class="ToDoTool">
        @item.ImgDataButton(DataButtonType.Delete, "../../Content/delete.jpg", null)
    </td>
</text>
)

The display item View Model is just a data item, it is not a Tracker<T> wrapper. The wrapper is handled automatically by the DataGrid.

We don’t need to put the <tr> tag in each data item: the container tag for each item is defined in the DataGrid helper and it is automatically inserted by the DataGrid. We have also the option to supply a delegate that returns a different item container as a function of the data item and of its position in the DataGrid.

It is worth discussing the two data buttons: the first one switches the row to edit mode, while the second one just deletes the row. In the example below an image button is used, but you can also use link and button helpers.

editTemplate
_S.H<ToDoView>(
@<text>         
     <td class="ToDo">
        @item.ValidationMessageFor(m => m.Name, "*")
        @item.TextBoxFor(m => m.Name)
     </td>
     <td class="ToDo">
        @item.ValidationMessageFor(m => m.DueDate, "*")
        @item.DateTimeFor(m => m.DueDate, DateTime.Today).Date()
     </td>
     <td class="ToDo">
        @item.ValidationMessageFor(m => m.Description, "*")
        @item.TextBoxFor(m => m.Description)
     </td>
     <td class="ToDoTool" colspan="2">
        @item.HiddenFor(m => m.id)
        @item.ImgDataButton(DataButtonType.Cancel, "../../Content/undo.jpg", null)
     </td>
</text>
)

The edit template is completely analogous to the display template. The only difference being that it contains input field allowing you to edit fields.

Please, notice the Hidden field containing the key! It is necessary! Here we have a cancel button that undoes all changes done to the data item and put the row in display mode again.

Last thing worth pointing out is the DateTimeFor helper that is able to take as input, date, time or date and time. It is able to read the DateRange attribute and to enforce its constraints. This means the user is allowed to insert just dates that conforms with the constraints. More information about the DateTimeFor Helper can be found here.

addDisplayTemplate
_S.H<ToDoView>(
               @<td colspan="5" class="ToDo">@item.ImgDataButton(DataButtonType.Insert, "../../Content/add.jpg", null)</td>
                  )

The insert template just contains an insert button that when clicked causes a new row to appear in edit mode.

gridTemplate
   _S.H<ToDoView>(
     @<table class="ToDo" >
       <tr>
       <td class="ToDoHeader"><strong>@item.SortButtonFor(m => m.Name, sortButtonStyle: SortButtonStyle.Button)</strong></td>
       <td class="ToDoHeader"><strong>@item.SortButtonFor(m => m.DueDate, sortButtonStyle: SortButtonStyle.Button)</strong></td>
       <td class="ToDoHeader"><strong>@item.ColumnNameFor(m => m.Description)</strong></td>
       <td class="ToDoHeader"><strong></strong></td>
       <td class="ToDoHeader"><strong></strong></td>
       </tr>
       @item.ViewData["Content"]
   </table>
)

It defines the look of the container of all items. In our case it just displays the <table> tag and the header of the table. The ColumnNameFor helper displays the name of a column, taking it from the Display attribute(ShortName if available, otherwise Name).

The SortButtonFor helper renders sort buttons on the columns where sorting is allowed. They can be used only together with the EnableSortingFor helper that we will discuss below.

The @item.ViewData[“Content”] construct  defines where all data items have to be inserted. It is a kind of placeholder and it needs to be inserted “as it is” in any template that describes a datagrid container.

It is worth pointing out that this template is passed an empty data item object to help the automatic construction of the container. Specifically, we can use reflection to extract all columns and we can also automatically decide some facts about the look of the container by extracting the attributes of each data item property (as for instance the display attribute).

The Datagrid

Summing up the whole call to the DataGridFor helper is:

@Html.DataGridFor(m => m.ToDoList, ItemContainerType.tr,
            _S.H<ToDoView>(
            @<text>         
                 <td class="ToDo">
                    @item.ValidationMessageFor(m => m.Name, "*")
                    @item.TextBoxFor(m => m.Name)
                 </td>
                 <td class="ToDo">
                    @item.ValidationMessageFor(m => m.DueDate, "*")
                    @item.DateTimeFor(m => m.DueDate, DateTime.Today).Date()
                 </td>
                 <td class="ToDo">
                    @item.ValidationMessageFor(m => m.Description, "*")
                    @item.TextBoxFor(m => m.Description)
                 </td>
                 <td class="ToDoTool" colspan="2">
                    @item.HiddenFor(m => m.id)
                    @item.ImgDataButton(DataButtonType.Cancel, "../../Content/undo.jpg", null)
                 </td>
            </text>
            ),
             _S.H<ToDoView>(
            @<text>         
                <td class="ToDo">
                    @item.ValidationMessageFor(m => m.Name, "*")
                    @item.DisplayField(m => m.Name)
                </td>
                <td class="editor-field">
                    @item.ValidationMessageFor(m => m.DueDate, "*")
                    @item.DisplayField(m => m.DueDate)
                </td>
                <td class="ToDo">
                    @item.ValidationMessageFor(m => m.Description, "*")
                    @item.DisplayField(m => m.Description)
                </td>
                <td class="ToDoTool">
                    @item.DetailLink(Ajax, "Edit Details", DetailType.Edit, "ToDoSubTasks", "Home",
                        new {
                            id = item.ViewData.Model.id},
                                            null)
                    @item.ImgDataButton(DataButtonType.Edit, "../../Content/edit.jpg", null)
                
                </td>
                <td class="ToDoTool">
                    @item.ImgDataButton(DataButtonType.Delete, "../../Content/delete.jpg", null)
                </td>
            </text>
            ),
            _S.H<ToDoView>(
              @<table class="ToDo" >
                <tr>
                <td class="ToDoHeader"><strong>@item.SortButtonFor(m => m.Name, sortButtonStyle: SortButtonStyle.Button)</strong></td>
                <td class="ToDoHeader"><strong>@item.SortButtonFor(m => m.DueDate, sortButtonStyle: SortButtonStyle.Button)</strong></td>
                <td class="ToDoHeader"><strong>@item.ColumnNameFor(m => m.Description)</strong></td>
                <td class="ToDoHeader"><strong></strong></td>
                <td class="ToDoHeader"><strong></strong></td>
                </tr>
                @item.ViewData["Content"]
            </table>
         ),
         _S.H<ToDoView>(
               @<td colspan="5" class="ToDo">@item.ImgDataButton(DataButtonType.Insert, "../../Content/add.jpg", null)</td>
                  ))

The first argument of the helper, as usual, defines the property to display in the DataGrid. The second property defines the kind of item container to be used (in our case a <tr>), and the last ones are the templates we discussed before.

There are also optional arguments to define html attributes(also as a function of the data item) and to pass a function to change dynamically the item container.

Finally, the pager is composed of various parts that can be used also  separately. Here I used link buttons but one can use also image or normal buttons:

  <div class="ToDoPager">
             @{ var pager = Html.PagerFor(m => m.CurrPage, m => m.PrevPage, m => m.TotalPages);}
             @pager.PageButton("<<", PageButtonType.First, PageButtonStyle.Link)
             @pager.PageButton("<", PageButtonType.Previous, PageButtonStyle.Link)
             @pager.PageChoice(5)
             @pager.PageButton(">", PageButtonType.Next, PageButtonStyle.Link)
             @pager.PageButton(">>", PageButtonType.Last, PageButtonStyle.Link)
             @pager.PageButton("Go To", PageButtonType.GoTo, PageButtonStyle.Button)
             @pager.GoToText(new { style = "width:50px;" })
</div>

The first call gets an object to be used to render all parts. The PageChoice method displays five page links before the current page, 5 page links after the current page and the number of the current page. There are buttons for the next page, last page, etc., and also a button plus a textbox to jump to any page.

Sorting

The first step to enable sorting with a mouse click on the columns is the insertion of a new property in our ViewModel to receive sorting information:

public List<KeyValuePair<LambdaExpression, OrderType>> ToDoOrder { get; set; }

The toolkit datagrid is able to exchange directly the lambda expressions to be used in LINQ queries with the Controller. Thus, we use a list of couples LambdaExpression OrderType. Where OrderType is an enumeration that specifies ascending or descending order. The whole list specifies a lexicographic sorting that can be based also on several columns. As previously discussed, sorting information can be used directly with LINQ expressions by means of the IEnumerable and IQueryable extension ApplyOrder defined in the namespace MVCControlsToolkit.Linq , .

It is worth pointing out that the sorting information come from the client, therefore a malicious user might try a denial of service attack by sending a manipulated sorting request involving  columns that are too difficult to sort (columns with no indexes defined on them, for instance). In order to defend ourselves from such an attack the Transformation Handler that receives the data from the DataGrid automatically discards columns that are not decorated with the CanSortAttribute that is defined in the MVCControlsToolkit.DataAnnotations namespace.

Sorting is defined by the user through the column sort buttons we have already seen in the grid header. By default, sort buttons do not cause a post. However they have a parameter to require an immediate post. When a new sorting is applied if there is a pager operating on the grid the page is automatically reset to the first page.

The up and down arrows of the sort buttons are defined in CSS classes specified in the sorting helper:

@Html.ManipulationButton(ManipulationButtonType.ResetGrid, "Reset", m => m.ToDoList, null, ManipulationButtonStyle.Button)
        @Html.EnableSortingFor(m => m.ToDoList, m => m.ToDoOrder, "NormalHeaderToDo", "AscendingHeaderToDo", "DescendingHeaderToDo", page: m => m.CurrPage)

In order to do its job the EnableSortingFor helper needs the collection to be sorted, the property that will contain all sorting information and also the page property. As the sort behavior of the column changes, the three CSS classes specified in the EnableSortingFor helper are applied to the buttons in order to change their look.

Another interesting feature is the ManipulationButtonType.ResetGrid that undoes all changes done to the datagrid that are not yet committed. Here commitment means commitment to a database or to any other storage, not simply a post: the grid remembers its previous values through several posts! We declare that commitment took place either by calling the Confirm method of a Tracker<Item> associated to a row or by simply reloading the grid with fresh data.

In order to undo a single row delete we have introduced the undelete data button and a template to substitute deleted rows. The undelete is easy: just put the undelete button in this template! However I prefer seeing my rows disappear completely! Therefore I have not used this feature in this example (no panic….in case of errors we have the reset button..).

That’s all! The deveoper’s that don’t want to add each time, pagers, sort buttons, filters, etc to their DataGrids can use Theming to define once and for all the look and features of their DataGrids,…or they can simply modify the DataGrid Theme I already defined in the RazorThemedGrid file in the download area. A tutorial on theming is here.

Stay Tuned !

Francesco

Tags: , , , , , , ,

Apr 24 2011

Designing a Themed Control in the Mvc Controls Toolkit

Category: MVCFrancesco @ 07:09

Mvc Controls Toolkit Datagrid Updated Tutorial (more recent version of Defining MVC Controls 2: Using the DataGrid)

Advanced Data Filtering Techniques in the Mvc Controls Toolkit

Defining MVC Controls 3: Datagrid, Sorting, and Master-Detail Views

All controls of the Mvc Controls Toolkit are designed to allow the maximum flexibility. For instance, the DataGrid is not table based but allows a generic template to be used as item template. Other controls,such as the DateTimeInput, and the DualSelectBox are composed of several parts that can be rendered separately. Features like, Sorting, Paging and Filtering are not included in controls like the DataGrid and the SortableList but are provided through separate helpers. Finally, all controls can be styled with Css. While this approach ensures an high level of flexibility, the time needed to set-up completely a control is higher compared to the time needed to setup a pre-configured control.

In order to promote re-usability of efforts made to set up a control, the Mvc Controls Toolkit allow the definition of Themes. Each Theme is composed of a Css enriched with an image folder, and of a set of Partial Views. Each Partial View features an already set-up control. While the layout and all parts each control is composed of are defined in the Partial Views, the Css define completely the style of all controls. Thus, the controls of each theme are ready to be used, with no further effort; we just need to pass data to them! Better configuration and style options are offered by the commercial version of the Mvc Controls Toolkit.

In this post I will show how to design a control to be inserted into a theme. I assume a basic knowledge of the Theming features of the Mvc Controls Toolkit. Therefore, readers are encouraged to read the documentation page about theming here before reading this post.

We will call “Test” the theme we are going to define, and we will analyze just how to design a Table based Themed Datagrid offering paging, sorting and column filtering services.,

As a first step we set-up our folders as shown below:

css_folder_treefolder_tree

Now let open the DataGrid.cshtml file. The Themed Datagrid is invoked by the helper:

  1. public static MvcHtmlString ThemedDataGridFor<M, TItem>(
  2.             this HtmlHelper<M> htmlHelper,
  3.             Expression<Func<M, List<Tracker<TItem>>>> expression,
  4.             GridFeatures gridFeatures,
  5.             Columns<TItem> fields,
  6.             Expression<Func<M, List<KeyValuePair<LambdaExpression, OrderType>>>> orderExpression = null,
  7.             Expression<Func<M, int>> page=null,
  8.             Expression<Func<M, int>> prevPage=null,
  9.             Expression<Func<M, int>> pageCount=null,
  10.             Expression<Func<M, Expression<Func<TItem, bool>>>> filter=null,
  11.             string title=null,
  12.             string name = "DataGrid"
  13.             )
  14.             where TItem:class, new()

expression defines the collection to be rendered in the Grid, filter will collect the filtering criteria (see here), orderExpression the sorting criteria(see here), and page, prevPage, and pageCount the paging (see here). gridFeatures is a bit flag enumeration that defines the desired features selected by the user of the Themed DataGrid:

[Flags]
    public enum GridFeatures {None = 0, Edit=1, Display=2, Insert=4, Delete=8, ResetRow=16, UndoEdit=32, InsertOne=64, Paging=128, Sorting=256, Filtering=512}

For more information see the Documentation page about theming.

While fields is a collection of column definitions. Each column contains the column features(if sorting, and filtering are allowed, and an optional column header to override the one provided through DataAnnotations), and possibly Edit and Display templates for the column. One can also define custom columns that are not connected with specific fields.For more information see the Documentation page about theming.

The ThemedDataGridFor helper just packs all information received into a GridDescription object defined as:

public class GridDescriptionBase
    {
        public GridFeatures Features { get; set; }
        public List<Column> Fields { get; set; }   
    }
    
    public class GridDescription:GridDescriptionBase
    {
        public dynamic ToShow {get; set;}
        public dynamic ToOrder { get; set; }
        public string Title { get; set; }
        public dynamic HtmlHelper { get; set; }
        public dynamic Page { get; set; }
        public dynamic PrevPage { get; set; }
        public dynamic PageCount { get; set; }
        public dynamic Filter { get; set; }

    }

Then it passes this object to our DataGrid.cshtml Partial View into: ViewData["ThemeParams"]

Thus our first step is to “unpack” this object:

@{
    var options = ViewData["ThemeParams"] as GridDescription;

    Func<dynamic, HelperResult> editTemplate = null;
    if ((options.Features & GridFeatures.Edit) == GridFeatures.Edit)
    {
        editTemplate = EditItem;
    }
    Func<dynamic, HelperResult> displayTemplate = DisplayItem;
    Func<dynamic, HelperResult> insertTemplate = null;
    if ((options.Features & GridFeatures.Insert) == GridFeatures.Insert)
    {
        insertTemplate = InsertItem;
    }
}

The above instruction just verifies if the Insert and Edit services are required, and if they are required assign the name of the Insert template(InsertItem), and of the Edit template(EditItem) to the variables inserItem, and editItem. The Display template, that is not optional, is always put into the displayItem variable.

Templates are defined through Razor helpers(see the documentation about templates) that use the columns information provided by the GridDescription class to render each single item.

Below the Insert template that just renders an insert button:

@helper InsertItem(dynamic htmlHelper)
    {
        var options = htmlHelper.ViewData["ThemeParams"] as GridDescription;
    int count = 0;
    bool hasCustomField = false;
    foreach (Column column in options.Fields)
    {
        if ((column.Features & FieldFeatures.Hidden) != FieldFeatures.Hidden)
        {
            count++;
        }
        else if (column.DispalyTemplate != null)
        {
            hasCustomField = true;
        }
    }
    if ((options.Features & GridFeatures.Edit) == GridFeatures.Edit
        || hasCustomField
        || (options.Features & GridFeatures.Delete) == GridFeatures.Delete) { count++; }
    <td colspan='@count' class="Theme-DataGrid-Column">
        @DataGridHelpers.ImgDataButton(
            htmlHelper, DataButtonType.Insert,
            Url.Content("~/Content/themes/test/images/add.jpg"), null)</td>
}

 

 

 

Let’s forget for just a minute about the hasCustomField variable, we will discuss about it when analyzing the Display template.The foreach loop just counts the number of columnsto be inserted in the colspan to format properly the table.If the grid is required to work also in Edit mode or if it is required to allow row deletes we adds one column more for the some command buttons. Columns marked as hidden are jumped since they contains just hidden field that will not be rendered together with the other columns.

The imgDataButton helper that renders the insert button takes an image form the Css that is part of the “Test” theme. Its is rendered in a quite strange way, namely,  it is not invoked as an extension method but just as a normal static method of the DataGridHelpers class. This is because we are using dynamic  variables(see the GridDescription definition) to handle Types that will be known just a run-time since our DataGrid is required to work with any class. In such a case extension methods cannot be used!

In the Display template we do some initialization and then we start a foreach loop on all columns:

@helper DisplayItem(dynamic htmlHelper)
    {
        var options = htmlHelper.ViewData["ThemeParams"] as GridDescription;
        bool hasCustomField=false;
        foreach (Column column in options.Fields)

We will see what the hasCustomField variable is needed for in a short time, let’s see first how “normal” columns(the ones that are not marked as Hidden) are dealt with:

if ((column.Features & FieldFeatures.Hidden) != FieldFeatures.Hidden)
            {
            <td class="Theme-DataGrid-Column">
            @{
                if (column.DispalyTemplate == null)
                {
                      @DisplayExtensions.DisplayFor(htmlHelper, column.Field)
                }
                else
                {
                      @CoreHTMLHelpers.TemplateFor(htmlHelper, column.DispalyTemplate)
                }
             }
            </td>
            }

 

Very simple: if the user has provided a Display template for that column we just invoke it through the TemplateFor helper otherwise we simply invoke the standard Mvc DisplayFor helper. It is worth to point out that column templates are passed information on the whole row, since we passed the htmlHelper for the whole row to the TemplateFor helper. This way, each column can use information about other columns in the rendering. Moreover, we may define “custom” columns that are associated to no specific field by by using  m => m as filed selector.

Now let’s see what happens to fields marked as Hidden:

else if(column.DispalyTemplate != null){
                hasCustomField = true;
            }

If they have a custom display template we just set the hasCustomField variable, defined at the beginning of the helper to true, just to remember we have found one of them. We have done the same thing in the Insert template. Why?? Simple! Because hidden fields are rendered in the edit Templates, since they just store data for a future post, thus a display template associated with an hidden field for sure is needed to render a command button. Probably a command button that uses the principal key of the row to render either a detail view of the record or some other children objects by means of either an action link or an Ajax call. Therefore, in such a case we need to display a further column reserved for all command buttons:

if ((options.Features & GridFeatures.Edit) == GridFeatures.Edit
            || hasCustomField
            || (options.Features & GridFeatures.Delete) == GridFeatures.Delete)
        {
        <td>
            <table>
                <tr>
                    @if ((options.Features & GridFeatures.Edit) == GridFeatures.Edit)
                    {         
                        <td>
                            @DataGridHelpers.ImgDataButton(
                                htmlHelper, DataButtonType.Edit,
                                Url.Content("~/Content/themes/test/images/edit.jpg"), null)
                        </td>
                    }
                    @if ((options.Features & GridFeatures.Delete) == GridFeatures.Delete)
                    {
                        <td>
                            @DataGridHelpers.ImgDataButton(
                                htmlHelper, DataButtonType.Delete,
                                Url.Content("~/Content/themes/test/images/delete.jpg"), null)
                        </td>
                    }
                    @if (hasCustomField)
                    {
                        foreach (Column column in options.Fields)
                        {
                            if ((column.Features & FieldFeatures.Hidden) == FieldFeatures.Hidden &&
                                column.DispalyTemplate != null)
                            {
                                <td>
                                    @CoreHTMLHelpers.TemplateFor(htmlHelper, column.DispalyTemplate)
                                </td>
                            }
                        }
                    }
               </tr>
            </table>
        </td>
        }

The Edit template is completely analogous, just the command buttons are different:

@helper EditItem(dynamic htmlHelper)
    {
        var options = htmlHelper.ViewData["ThemeParams"] as GridDescription;

        foreach (Column column in options.Fields)
        {
            if ((column.Features & FieldFeatures.Hidden) != FieldFeatures.Hidden)
            {
            <td class="Theme-DataGrid-Column">
            @{
                if (column.EditTemplate == null)
                {
                      @EditorExtensions.EditorFor(htmlHelper, column.Field)
                }
                else
                {
                    if (column.EditTemplate is string)
                    {
                        string templateName = column.EditTemplate as string;
                        templateName = "Themes/Test/" + templateName;
                        @CoreHTMLHelpers.TemplateFor(htmlHelper, templateName)
                    }
                    else
                    {     
                        @CoreHTMLHelpers.TemplateFor(htmlHelper, column.EditTemplate)
                    }
                }
             }
            </td>
            }
        }
        <td>
            <table>
                <tr>          
                    <td>
                        @DataGridHelpers.ImgDataButton(
                            htmlHelper,
                            DataButtonType.Cancel,
                            Url.Content("~/Content/themes/test/images/undo.jpg"), null)
                    </td>
                    @if ((options.Features & GridFeatures.UndoEdit) == GridFeatures.UndoEdit)
                    {
                        <td>
                            @DataGridHelpers.LinkDataButton(
                                htmlHelper,
                                DataButtonType.ResetRow,
                                ThemedControlsStrings.Get("Item_ResetRow", "DataGrid"), null)
                        </td>
                    }
                    @foreach (Column column in options.Fields)
                    {
                        if ((column.Features & FieldFeatures.Hidden) == FieldFeatures.Hidden)
                        {
                            if (column.EditTemplate != null)
                            {
                                @CoreHTMLHelpers.TemplateFor(htmlHelper, column.EditTemplate)
                            }
                            else
                            {
                                <td style="width:0px">
                                    @InputExtensions.HiddenFor(htmlHelper, column.Field)
                                </td>
                            }
                        }
                    }
               </tr>
            </table>
        </td>
}

It is convenient to define also a Razor helper that renders the Header of the table, with all column names, sort, and filtering logics:

@helper DisplayHeader(dynamic htmlHelper, GridDescription options)
    {
    <tr>
        @{bool hasCustomField=false;}
        @foreach (Column column in options.Fields)
        {
            if ((column.Features & FieldFeatures.Hidden) != FieldFeatures.Hidden)
            {
            <td class="Theme-DataGrid-Header">
                <table>
                <tr>

The above Razor Helper is completely analogous to the other templates. In each column we have 2 sections. The first one is dedicated to filtering and the second one is dedicated either to a sort button with the column name inside it or just to the column name if the column is not sortable.

Let’s start with the filtering:

@if ((options.Features & GridFeatures.Filtering) == GridFeatures.Filtering && (column.Features & FieldFeatures.Filtering) == FieldFeatures.Filtering)
                {
                    <td >
                    <div class="Theme-DataGrid-Filter">
                        <div class="MvcControlsToolkit-Hover">
                            @{
                            var h1 = DataFilterClauseHelpers.DataFilterClauseFor(
                                htmlHelper,
                                options.Filter,
                                column.Field,
                                "first");
                            var h2 = DataFilterClauseHelpers.DataFilterClauseFor(
                                htmlHelper,
                                options.Filter,
                                column.Field,
                                "second");
                            bool oldClientSetting = ViewContext.ClientValidationEnabled;
                            ViewContext.ClientValidationEnabled = false;
                                }
                              <table>
                                <tr>
                                    <td>
                                        @InputExtensions.CheckBox(h1, "Selected", h1.ViewData.Model.Selected)
                                    </td>
                                    <td>
                                        @DataFilterClauseHelpers.FilterClauseSelect(h1, h1.ViewData.Model.Condition, column.Field)
                                    </td>   
                                </tr>
                                <tr>
                                    <td colspan="2">
                                        @{object val1=h1.ViewData.Model.Search;
                                          if (! h1.ViewData.Model.Selected)
                                          {
                                              val1 = string.Empty;
                                          }
                                        }
                                        @InputExtensions.TextBox(h1, "Search", val1)
                                        @{ValidationExtensions.Validate(h1, "Search"); }
                                    </td>
                                </tr>
                              </table>
                              <table>
                                <tr>
                                    <td>
                                        @InputExtensions.CheckBox(h2, "Selected", h2.ViewData.Model.Selected)
                                    </td>
                                    <td>
                                        @DataFilterClauseHelpers.FilterClauseSelect(h2, h2.ViewData.Model.Condition, column.Field)
                                    </td>   
                                </tr>
                                <tr>
                                    <td colspan="2">
                                        @{object val2=h2.ViewData.Model.Search;
                                          if (!h2.ViewData.Model.Selected)
                                          {
                                              val2 = string.Empty;
                                          }
                                         }
                                        @InputExtensions.TextBox(h2, "Search", val2)
                                        @{ValidationExtensions.Validate(h2, "Search"); }
                                        @{ViewContext.ClientValidationEnabled=oldClientSetting;}
                                    </td>
                                </tr>
                              </table>    
                            </div>
                        </div>
                    </td>
                    
                }

Filters are implemented through an hover menu that appears on mouse hover a filtering icon. All hover menu logic is contained in the Css, so we don’t have to worry about this while coding the filtering logics. Each column may contains two filter clauses, this is the minimum to implement min-max conditions. Accordingly we create the two helpers h1 and h2 to renders the filters by means of the DataFilterClauseFor helper.

We use each helper to render a checkbox to enable the filter criterion, a dropdown to select the filtering condition, and finally a TextBox for inserting the Filter parameter and the associated validation helper. We ensure that if the filter is disabled the TextBox is empty.

What’s beautiful about the DataFilterClauseFor helper is that once we have Rendered input fields, for its “Search” field, for its filter criterion(our DropDown), and for its enabled condition…it handles all filtering logics for us….We will receive the complete filter obtained combining all columns filters in our the filter property of our ViewModel..So we need just to apply it to an IQueryable to filter it (see also here for more information).

Let’s move to the second section (sorting and column names):

<td>
                <strong>
                @if ((column.Features & FieldFeatures.Sort) == FieldFeatures.Sort)
                {
                    @DataGridHelpers.SortButtonForTrackedCollection(
                        htmlHelper,
                        options.ToShow,
                        column.Field,
                        sortButtonStyle: SortButtonStyle.Button)
                }
                else
                {
                    if (column.ColumnHeader != null)
                    {
                        @column.ColumnHeader
                    }
                    else
                    {
                       @DataGridHelpers.ColumnNameForTrackedCollection(
                       htmlHelper,
                       options.ToShow,
                       column.Field)
                    }
                }
            </strong>
            </td>

options.Toshow contains the lambda expression that defines the collection to be shown in the grid. If the column sorting is required we render a sort button otherwise we render just the column name either taken from Data Annotations or from the column definition.

For all columns marked as Hidden as usual we have:

else if (column.DispalyTemplate != null)
            {
                hasCustomField = true;
            }

and finally:

@if ((options.Features & GridFeatures.Edit) == GridFeatures.Edit
            || hasCustomField
            || (options.Features & GridFeatures.Delete) == GridFeatures.Delete)
        {
            <td class="Theme-DataGrid-Header"></td>
        }

If there is the column for the command buttons, we just render an empty <td> to have the right number of <td>.in the header.

Now we are ready to render the DataGrid:

<table>
@DisplayHeader(options.HtmlHelper, options)
@DataGridHelpers.DataGridFor(options.HtmlHelper,
    options.ToShow,
    ItemContainerType.tr,
    editTemplate,
    displayTemplate,
    null,
    insertTemplate,
    enableMultipleInsert: (options.Features & GridFeatures.InsertOne) != GridFeatures.InsertOne,
    itemCss: "Theme-DataGrid-ItemCss",
    altItemCss: "Theme-DataGrid-AlternateItemCss",
    toTrack: options.GetToTrack())
</table>

toTrack contains the list of all properties we need to save in hidden fields for the changes tracking performed by the grid. This argument is optional, but if we don’t pass it the DataGrid helper just save the original values of all properties of each item. Since, the list of all properties we are using can be easily computed from the columns definition, we get it by calling the GridDescription class method GetToTrack().

Finally we add Pager, and Sorting helper if these services are required:

@if ((options.Features & GridFeatures.Paging) == GridFeatures.Paging)
{
    <div class="Theme-DataGrid-Pager">
        @{ var pager = PagerHelper.PagerFor(options.HtmlHelper, options.Page, options.PrevPage, options.PageCount);}
        @pager.PageButton(ThemedControlsStrings.Get("Page_First", "DataGrid"), PageButtonType.First, PageButtonStyle.Link)
        @pager.PageButton(ThemedControlsStrings.Get("Page_Prev", "DataGrid"), PageButtonType.Previous, PageButtonStyle.Link)
        @pager.PageChoice(5)
        @pager.PageButton(ThemedControlsStrings.Get("Page_Next", "DataGrid"), PageButtonType.Next, PageButtonStyle.Link)
        @pager.PageButton(ThemedControlsStrings.Get("Page_Last", "DataGrid"), PageButtonType.Last, PageButtonStyle.Link)
    </div>
}

@if (((options.Features & GridFeatures.Sorting) == GridFeatures.Sorting) && options.ToOrder != null)
{
        @DataGridHelpers.EnableSortingFor(
            options.HtmlHelper, options.ToShow,
            options.ToOrder, "Theme-DataGrid-NormalHeader",
            "Theme-DataGrid-AscendingHeader", "Theme-DataGrid-DescendingHeader",
            page: options.Page)
}

The whole code can be downloaded from the download page of the Mvc Controls Toolkit here.

That’s all! Not so difficult, isn’t it?

The full code is contained in the RazorThemedGrid file in the Mvc Controls Toolkit download page. Download it and enjoy!

                                                    Stay Tuned

                                                                 Francesco

Tags: , , , , ,

Feb 6 2011

Data Filtering, in the New Mvc 3 Version of the Mvc Controls Toolkit

Category: Entity Framework | MVC | Asp.netFrancesco @ 05:11

See also an updated version of this post:  Advanced Data Filtering Techniques in the Mvc Controls Toolkit

Mvc Controls Toolkit Datagrid Updated Tutorial (updated version of Defining MVC Controls 2: Using the DataGrid)

Defining MVC Controls 3: Datagrid, Sorting, and Master-Detail Views

The Mvc Controls Toolkit offers an interesting data filtering feature: the controller can receive directly a LinQ expression defining the filtering criteria chosen by the user when a view is posted. This way the user can choose among several filtering options by clicking buttons, or selecting checkboxes and then filling the input fields of the selected filtering options. No need to define ViewModel properties for each of the available options, the action method of the controller receives always the same data structure: a LinQ Expression. New filtering options can be easily added modularly with the no need to modify the controller and the code behind it. This increases modularity and makes easier  software maintenance.

Let see how this works in practice with the help of the same example used in my previous posts about the Mvc Controls Toolkit library(see the links next to the title). The whole code used in this example can be downloaded here(the file named BasicTutorialsCode), while screenshots of the software running are here. .

First of all we add the property destined to contain the LinQ expression to the ViewModel:

         public int TotalPages { get; set; }
        public int CurrPage { get; set; }
        public int PrevPage { get; set; }
        public List<Tracker<ToDoView>> ToDoList {get; set;}
        public List<KeyValuePair<LambdaExpression, OrderType>> ToDoOrder { get; set; }
        public System.Linq.Expressions.Expression<Func<ToDoView, bool>> ToDoFilter { get; set; }

The LinQ Expression is a map from ToDoView, that is the class the filter will be applied to, and bool, since formally it defines a function that verifies if an instance of ToDoView satisfies the criterium of the filter.

Now we can use this expression directly in the method that retrieves the items:

if (filter == null)
                {
                    result = context.ToDo.Select(item =>
                        new ToDoView() { Name = item.Name, Description = item.Description, DueDate = item.DueDate, id = item.id }).ApplyOrder(order).Select(viewItem =>
                        new Tracker<ToDoView>
                                {
                                    Value = viewItem,
                                    OldValue = viewItem,
                                    Changed = false
                                }).Skip(toSkip).Take(pageDim).ToList();
                }
                else
                {
                    result = context.ToDo.Select(item =>
                        new ToDoView() { Name = item.Name, Description = item.Description, DueDate = item.DueDate, id = item.id }).Where(filter).ApplyOrder(order).Select(viewItem =>
                        new Tracker<ToDoView>
                        {
                            Value = viewItem,
                            OldValue = viewItem,
                            Changed = false
                        }).Skip(toSkip).Take(pageDim).ToList();
                }

The code above shows that it was enough to add a Where(filter) instruction to our original code to get the filtered data.

Now we need to define a class for each filtering option. For sake of semplicity let just define a single filtering option. Our class needs just to implement an interface:

public interface IFilterDescription<TData>
    {
        Expression<Func<TData, bool>> GetExpression();
    }

The GetExpression function returns the actual Filter. The input fields that the user is required to fill are represented by properties of this class, and are used in the implementation of GetExpression():

public class ToDoItemByNameFilter: 
        IFilterDescription<ToDoView>
    {
        [Required]
        [Display(Prompt="chars the name of item starts with")]
        public string Name {get; set;}
        public System.Linq.Expressions.Expression<Func<ToDoView, bool>> GetExpression()
        {
            System.Linq.Expressions.Expression<Func<ToDoView, bool>> res = null;
            Name=Name.Trim();
            if (!string.IsNullOrEmpty(Name))
            {
                Name=Name.Trim();
                res= m => (m.Name.StartsWith(Name));
                
            }
            return res;
        }
    }

In our case we would like to select all items whose Name field starts with the characters inserted in the Name property defined in our ToDoByNameFilter class.

We just Trim our input and then we use it in the LinQ expression returned by GetExpression.

Our ToDoItemByNameFilter plays also the role of ViewModel for a partial view that takes care of the user interface for our filter, so we can decorate its Name property with attributes defining both validation and appearance constraints. In our case we defined a WatermarK through the Prompt property of the Display attribute.

In order to make the watermark actually apppears and the textbox add some adequate formatting we can use the TypedTextBox of the Mvc Controls Toolkit in the partial view that defines the graphical appearance of our filter:

<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<Mvc_Examples.Controls.ToDoItemByNameFilter>" %>
<%@ Import Namespace=" MVCControlsToolkit.Core" %>
<%@ Import Namespace=" MVCControlsToolkit.Controls" %>
<%: Html.TypedTextBoxFor(m => m.Name, watermarkCss:"watermark") %>

Now it remains just to insert the helper of the filter in our View. In order to let the user selects among several filters we can use the ViewList defined in the Mvc Controls Toolkit. This way either by clicking some mutual exclusive checkboxes or by clicking some button, the user let the Partial View associate to a Filter to appear. In our case for sake of simplicity we give to the user just the choice between our previous Name filter and no filter at all:

<div >
    <%: Html.ViewList("ToDoFilter", "ToDoFilterSelected") %> 
        <input id="Checkbox1" type="checkbox" class = 'ToDoFilter_checkbox ByNameFilter_checkbox'/>  &nbsp; Filter by name 
        <span id='ByNameFilter' class='ToDoFilter'><%:Html.DataFilter(m => m.ToDoFilter, 
                                new Mvc_Examples.Controls.ToDoItemByNameFilter(),
                                           "ToDoFilterByName")%></span>  
    </div>
    <div >
    <input id="Checkbox2" type="checkbox" class = 'ToDoFilter_checkbox NoFilter_checkbox'/>  &nbsp; NoFilter
    <span id='NoFilter' class='ToDoFilter'></span>
    </div>

The arguments of our DataFilter helper are just an expression that selects the ViewModel property to fill with the filtering expression, an instance of the class that defines the filter, and the name of the Partial View that we defined before.

The ViewList helper selects one of two spans, one contains the filter helper and the other is simply empty. The selection is done with two checkboxes.Details on how to use of the VieList can be found in the documentation here.

By adding a new argument to our DetailView Helper we can make also our detail view appears in a jQuery UI dialog:

<% Html.DetailFormFor(Ajax, m => m.ToDoList, ExternalContainerType.div,
           "ToDoSubTasks", "Home", null, "isChangedToDo", "isDeletedToDo", detailDialog:
           new MVCControlsToolkit.Controls.DataGrid.Dialog
           {
               Title = "prova dialogo",
               Show = "slide",
               Hide = "slide",
               MinWidth=800

           });%>
</asp:Content>

THAT’S ALL!  Download the code and enjoy!

                             

                                       Stay Tuned!

                                               Francesco

Tags: , , , , , ,

Nov 15 2010

Defining MVC Controls 3: Datagrid, Sorting, and Master-Detail Views

Category: Asp.net | Entity Framework | MVCFrancesco @ 00:15

Defining MVC Controls 1

Mvc Controls Toolkit Datagrid Updated Tutorial

Advanced Data Filtering Techniques in the Mvc Controls Toolkit

I am back with the second tutorial about using the Datagrid of the  MVC Controls Toolkit . We are going to modify the the example of my previous post to include sorting on a mouse click on the columns.

The code of this tutorial is containe in the download page of MVC Controls Toolkit, that is here and is named BasicTutorialsCode.

As a first step we need a new parameter in our View Model to exchange sorting information with the View:

public List<KeyValuePair<LambdaExpression, OrderType>> ToDoOrder { get; set; }

The toolkit datagrid is able to exchange directly the lambda expressions to be used in the Linq queries with the Controller. Thus, we use a list of couples Lambda Expression OrderType. Where OrderType is an enumeration that specifies ascending or descending order. The whole list specifies a lexicographic sorting that is possibly based on several columns.

MVC Controls Toolkit defines extension methods to apply directly the above list either to  an IEnumerable or to an IQueryable.It is just to include the namespace: MVCControlsToolkit.Linq and any IEnumerable or IQueryable will be enriched with the method ApplyOrder that accepts the above list as argument. If an ordering is already defined on either the IEnumerable or the IQueryable the new sorting will be chained Lexicographically with it.  

Now our paged search query becomes:

result = context.ToDo.Select(item =>
                    new ToDoView() { Name = item.Name, Description = item.Description, DueDate = item.DueDate, id = item.id }).ApplyOrder(order).Select(viewItem =>
                    new Tracker<ToDoView>
                            {
                                Value = viewItem,
                                OldValue = viewItem,
                                Changed = false
                            }).Skip(toSkip).Take(pageDim).ToList();

It is worth to point out that the sorting information comes from the client, therefore a malicious user might try a denial of service attack by sending a manipulated request of sorting on a column that is too  difficult to sort (a column with no index defined on it, for instance). In order to defend ourselves from a similar attack the Transformation Handler that receives the data from the DataGrid automatically discard columns that are not decorated with the CanSortAttribute that is defined in the MVCControlsToolkit.DataAnnotations namespace. In our case we have the following Data annotations:

        [Required, CanSort, Display(Name="Name")]
        public object Name { get; set; }
        [Required, Display(ShortName = "Description")]
        public object Description { get; set; }
        [CanSort, Display(ShortName = "Due Date"), Format(DataFormatString="{0:D}")]
        public object DueDate { get; set; }

The DisplayAttribute is a standard .Net. Our DataGrid uses ShortName or Name (if ShortName is not specified) for the header of both the unsortable and the sortable columns.The FormatAttribute  inherits from the standard .Net DisplayAttribute and extends it with some properties that we will use in the 0.8 release of the MVC Controls Toolkit, where we will define typed input fields. At moment it has the same behavior of its parent. In this example we use it to specify a nice format for the date.

Now our datagrid template becomes:

<table class="ToDo" >
<tr>
<td class="ToDoHeader"><strong><%:Html.SortButtonFor(m => m.Name, sortButtonStyle: SortButtonStyle.Button) %></strong></td>
<td class="ToDoHeader"><strong><%:Html.SortButtonFor(m => m.DueDate, sortButtonStyle: SortButtonStyle.Button) %></strong></td>
<td class="ToDoHeader"><strong><%: Html.ColumnNameFor(m => m.Description) %></strong></td>
<td class="ToDoHeader"><strong></strong></td>
<td class="ToDoHeader"><strong></strong></td>
</tr>
<%:ViewData["Content"] as MvcHtmlString %>
</table>

Where we can see the use of the sort buttons, and of the ColumnNameFor helper. As default, sort buttons do not  cause post-backs, however they have a parameter to require immediate post-back. Personally I prefer avoiding immediate post-back because this way I can set up my complete lexicographic sorting and only then I require a post-back to update my grid. In any case if there is a pager operating on the grid the change of the sorting causes the page to be reset to the first page automatically.

The up and down arrows of the sort buttons are defined in CSS classes specified in the sorting helper:

  <%:Html.DataGridFor(m => m.ToDoList, ItemContainerType.tr,  "ToDoEditItem",  "ToDoDisplayItem", "ToDoGrid", "ToDoInsertItem")%>
    </div>
    <div class="ToDoPager">
                    <% var pager = Html.PagerFor(m => m.CurrPage, m => m.PrevPage, m => m.TotalPages); %>
                    <%:pager.PageButton("<<", PageButtonType.First, PageButtonStyle.Link) %>
                    <%:pager.PageButton("<", PageButtonType.Previous, PageButtonStyle.Link) %>
                    <%:pager.PageChoice(5) %>
                    <%:pager.PageButton(">", PageButtonType.Next, PageButtonStyle.Link) %>
                    <%:pager.PageButton(">>", PageButtonType.Last, PageButtonStyle.Link) %>
                </div>
    <div>
    <input type="submit" value="Save" />
    <%:Html.ManipulationButton(ManipulationButtonType.ResetGrid, "Reset", m => m.ToDoList, null, ManipulationButtonStyle.Button) %>
    <%: Html.EnableSortingFor(m => m.ToDoList, m => m.ToDoOrder, "NormalHeaderToDo", "AscendingHeaderToDo", "DescendingHeaderToDo", page: m => m.CurrPage) %>
    <%:Html.HiddenFor(m => m.TotalPages) %>
To do its job the EnableSortingFor helper needs the collection, the sorting property and also the page property. As the sort behavior of the column changes, the three CSS classes specified in the EnableSortingFor helper are applied to the buttons in order to change their look.

Another new feature is the ManipulationButtonType.ResetGrid that undos all changes done to the datagrid and not yet committed. Here commitment means commitment to a database or to any other structure, not simply a post-back: the grid remembers its previous values through post-backs! We declare that commitment took place either by calling the Confirm method of a Tracker<Item> associated to a row or by simply reloading the grid with fresh data.

In order to undo a single row delete we have introduced the undelete data button and a template to substitute deleted rows. The undelete is easy: just put the undelete button in this template! However I prefer seeing my rows disappear completely! Therefore I have not used this feature in this example (no panic….in case of errors we have the reset button..).

The edit row template has not changed from our previous tutorial, but there are some changes in the display row template:

            <td class="ToDo">
                <%: Html.ValidationMessageFor(m => m.Name, "*")%><%: Html.DisplayField(m => m.Name) %>
            </td>
            <td class="editor-field">
                <%: Html.ValidationMessageFor(m => m.DueDate, "*")%><%: Html.DisplayField(m => m.DueDate)%>
            </td>
            <td class="ToDo">
                <%: Html.ValidationMessageFor(m => m.Description, "*")%><%:  Html.DisplayField(m => m.Description)%>
            </td>
            <td class="ToDoTool">
                <%:Html.DetailLink(Ajax, "Edit Details", DetailType.Edit, "ToDoSubTasks", "Home",
                    new { 
                        id = Model.id},
                                        null)%>
                <%: Html.ImgDataButton(DataButtonType.Edit, "../../Content/edit.jpg", null)%>
                
            </td>

The use of the DisplayField helper to display not editable fields not only ensures right formatting as the use of the DisplayFor standard Mvc helper, but also it enables fields representing the same data be synchronized automatically in the view! In particular it enables detail data retrieved via Ajax not only to display in a separate form but also to update the corresponding data in the master grid.

We have just introduced our next feature: the Master-Detail Ajax helper. Next to the Edit button that performs on line editing, there is also a Detail Link helper. In order to do its job this helper needs the Ajax object of the View, a name to put on the link, the name of an Action method returning a Partial View, the name of the associated Controller, and the route parameters. Moreover we need to specify also if the detail form we are going to render is a display or an edit form.

The Partial View returned by the Action method must contain neither an Ajax  nor a standard form: an Ajax form is already supplied by the Master Detail helper(this way we enhance re-usability because the same Partial View can be used with both Ajax and normal child calls):

<% Html.DetailFormFor(Ajax, m => m.ToDoList, ExternalContainerType.div,
           "ToDoSubTasks", "Home", null, "isChangedToDo", "isDeletedToDo");%>

The arguments passed to the helper are: the View Ajax object, the Master collection, the type of container where we woluld like to receive the Ajax content, an Action method and  a Controller to receive the post, some Html attributes and two CSS classes. The first class (in our case “isChangedToDo") is applied to the display data-field(the ones defined with the DisplayField helper) of the Master grid when they are changed because of the synchronization between detail form and Master data. The edit field of the grid are not updated because they contains new data provided by the user that this way can decide if continuing with  the change in the Master grid or if accepting the changes provided by the Ajax call.

Please note that the DetailFormHelper needs to be put out of the main form, don’t forget it!!!

The grid accepst also another optional row template to be used with rows that are updated because of the synchronization between detail and master View.

The second CSS class (in our case “isDeletedToDo")  is applied to a whole row when a data item retrieved by the Ajax call is discovered to be already deleted. If the user updates a deleted row a new row is created. Obviously the final choice is left to the Controller that may decide to abort the changes in a similar case.

In order to enhance re-usability of controllers (in particular of child controllers that returns Partial Views) we defined the [AcceptViewHint] Action Filters that enables a father view to require an action method of a controller uses a particular Partial View, in a way that is analogous to a client requiring that a Web Service uses a specific protocol or a client selecting a specific endpoint. The Partial View Hint is transmitted in either a Route parameter or a post parameter whose name is ViewHint.The name passed to the filter is scanned for acceptable length and may contain only alphanumeric characters in order to prevent attacks from malicious users.

I will not go into the code of the Detail View of the example that is completely analogous to the one of the Main View that we already discussed in detail in my previous post. The only things worth to note is the use of the SortableListFor helper to allows editing of the list of subtasks associated with a ToDo item. The SortableListFor helper allows delettion/in place editing/insertion of subtasks and allows also sorting of the subtasks by simply dragging them with the mouse .  The SortableListFor uses JQuery Sortable UI element, but transferring the order from the DOM into a collection of complex type on the server side….is not an easy task to accomplish.

Below the use of the helper:

<%: Html.SortableListFor(m => m.SubTasks, "SubTasksToSort", "SubTasksToSortAddItem", 0.7f,
                                        htmlAttributesContainer: new Dictionary<string, object> { { "class", "SortableList" } }
                    )%>

0.7f is the opacity used by the JQuery Sortable, the first argument is the collection to operate on, while “SubTasksToSort” is the Item template and “SubTasksToSortAddItem” is the template for inserting a new element.

Below the Item template:

<div id='<%: Html.PrefixedId("InnerContainer") %>'>
<%: Html.TextBoxFor(m => m.Name, new Dictionary<string, object> { { "class", "ToDoDetailName" } })%><%: Html.ValidationMessageFor(m => m.Name, "*") %>
<%: Html.TextBoxFor(m => m.WorkingDays, new Dictionary<string, object> {{"class", "ToDoDetailDuration"}})%><%: Html.ValidationMessageFor(m => m.WorkingDays, "*") %>
<%: Html.SortableListDeleteButton("Delete",  ManipulationButtonStyle.Link) %>
</div>

As one can see the SortableListFor helper has it own delete buttons.

Finally the Add Item template:

<div >
<%: Html.SortableListAddButton("Insert New", ManipulationButtonStyle.Link)%>
<span id='<%: Html.SortableListNewName() %>' style="visibility:hidden">
<%: Html.TextBoxFor(m => m.Name, new Dictionary<string, object> { { "class", "ToDoDetailName" } })%><%: Html.ValidationMessageFor(m => m.Name, "*") %>
<%: Html.TextBoxFor(m => m.WorkingDays, new Dictionary<string, object> {{"class", "ToDoDetailDuration"}})%><%: Html.ValidationMessageFor(m => m.WorkingDays, "*") %>
<%: Html.SortableListDeleteButton("Delete",  ManipulationButtonStyle.Link) %>
</span>
</div>

The Add Button of the SortableListFor needs a target container that it will make visible when it is pressed. We can specify it by giving the id returned by the helper

 Html.SortableListNewName() to a span, div or other container.

At moment we have finished……Next time we will speak about typed input fields and about the advanced filtering capabilities of the 0.8 release of the MVC Controls Toolkit.

                                          Stay Tuned……

                                           Francesco

For more information or consulences feel free to contact me,

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Oct 30 2010

Defining MVC Controls 2: Using the DataGrid

Category: MVC | Entity Framework | Asp.netFrancesco @ 00:46

See a more recent version of this tutorial: Mvc Controls Toolkit Datagrid Updated Tutorial

Defining MVC Controls 1

Defining MVC Controls 3: Datagrid, Sorting, and Master-Detail Views

Data Filtering, in the New Mvc 3 Version of the Mvc Controls Toolkit

This post is a tutorial un how to use the Update/Delete/Insert Templated datagrid of the MVC Controls Toolkit. You can download the full code used in this tutorial here (the package is named BasicTutorialsCode and it contains also the database)..

Our Data model is simply a Todo List with three fields: Name(varchar), Description(varchar) and DueDate(date), plus the principal key id of type identity. As first step we define the Database, and a table named ToDo  with the previous four fields.

Then, we create an entity framework model based on the database just created: I called it MeetingsModel because in a future post I will extend it with the management of a meeting room.

Now it is time to create a MetaClass to handle the constraints on our ToDo items. Let say that the Name and Description fields are required (i.e they can’t be null), while for the date we have a strange constraints: the DueDate can range from 1 month before today to 6 months after today. Since today is not a definite value such constraints can not be interpreted as a Data constraints, thus its natural place is not together with the other data constraints of the data layer: we will take care of it in a few minutes! First let take care of the the other simpler constraints, and add to our project a new file named Todo.cs just under the Models folder. What we put in this file is quite standard:


using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.ComponentModel.DataAnnotations;
using MVCControlsToolkit.DataAnnotations;

namespace Mvc_Examples.Models
{
    [MetadataType(typeof(MetaToDo))]
    public partial class ToDo
    {

    }
    public class MetaToDo
    {
        [Required]
        public object Name { get; set; }
        [Required]
        public object Description { get; set; }
        
    }
}

Now let go to the View Model! What we need to put into the View Model? For sure the ToDo items extracted from the database. However, we would like the items be paged, so we have to insert at least a Page property containing the current page. A single Page int is enough for the MVC Controls Toolkit pager to work, but for a better paging experience it is better to supply also the total number of pages. It is ok, our pager control handle also this information, if available.

Now…the user might edit some fields and then he might change page. What does we do if there are validation errors in its editing? The better thing to do is to go back to the previous page and force him to correct the errors. Therefore, we have to remember what page we come from. Thus we need also a previous page property in our View Model. Luckily we don’t need to put it in a hidden field because our pager already offers  this type of service when a “previous page” property is available.

Summing Up, our View Model needs the following properties: CurrPage, PrevPage, and TotalPages, plus a ToDoList property containing all ToDo items.

Now we have to decide how to handle the strange constraint on the DueDate. One way to do it is to define a View Model version of the ToDo class where we can apply it. In this case we might solve in a simpler way but I prefer to be more general:

using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.ComponentModel.DataAnnotations;
using MVCControlsToolkit.DataAnnotations;
 
namespace Mvc_Examples.Models
{
    [MetadataType(typeof(MetaToDo))]
    public partial class ToDoView
    {
        public int? id { get; set; }
 
        public string Name { get; set; }
 
        public string Description { set; get; }
 
        [DateRange(DynamicMinimum="MinDate", DynamicMaximum="MaxDate")]
        public DateTime DueDate {set;get;}
 
        [MileStone]
        public DateTime MaxDate
        {
            get 
            {
                return DateTime.Today.AddMonths(6);
            }
            set 
            {
            }
        }
 
        [MileStone]
        public DateTime MinDate
        {
            get 
            {
                return DateTime.Today.AddMonths(-1);
            }
            set 
            {
            }
        
        
        }
 
    }
}
 

Please notice that we have used the same MetaData class of the original ToDo class. This is important in order to avoid code duplications! As a general rule when building a View Model one has to use either the original data classes, or for each data class we define a modified version and use it as a son of the View Model: this way, we can use the same metaclasses. Please avoid putting fields from more than one data class into a single View Model Class. This can be done only if data are someway aggregated and transformed into other properties, otherwise it is better to keep a one to one correspondence between data classes and classes used in the View Model: this way we increase modularity and we can reuse the metadata classes of the original data classes(duplicating code always causes a lot of problems…).

We have defined two new properties MinData and MaxData that are always equal to Today minus one month and Today plus 6 months: they define the range of possible values for the DueDate property.

The Milestone attribute that decorates these two properties is defined in the MVCControlsToolkit.DataAnnotations namespace and it do exactly nothing…

It is just an hint for the View not to put these properties  into input fields  because their only purpose in the View is giving help to the user: the view designer can use them to display a message for the user, for example.

Our constraint on the DueDate is enforced by using the DateRange attribute defined in the MVCControlsToolkit.DataAnnotations namespace. This attribute act very similarly to the normal Range validation attribute, but accepts also dynamic minimum and maximum, that are essentially the names of the properties containing the actual minimum and maximum.

Next step is the design of the data access procedures. It is not a good idea to insert them into the controller methods, because they might be useful to more than one controller, and because it is always better to keep the data layer separate from the controllers layer. We will put them as static methods of our View Model that this way becomes a kind of  a standard for accessing ToDo items(we will use it always when paged ToDo items are needed). This choice is acceptable for this application, but in different situations we might have introduced a new class.

Therefore our View Model now contains the properties we discussed before:

        public int TotalPages { get; set; }
        public int CurrPage { get; set; }
        public int PrevPage { get; set; }
        public List<Tracker<ToDoView>> ToDoList {get; set;}

Plus two static methods, say GetToDoPage and UpdatePage, respectively for retrieving one page of data, and for passing to the database the updates made by the user to one page of data.

In order to help passing changes to the database the MVC Controls Toolkit furnishes the class Tacker<T> that is a wrapper to put around a data item. It maintains two versions of the data item, the original version and the one with the changes applied by the user. Moreover, it has also a Boolean value Changed to signal that the two versions are different.

Comparison between the two versions yields easily the operation to be done on the database:

  • Old version null and new version different from null: we have an insertion
  • Old version different from null and new version null: we have a deletion
  • Both versions different from null: we have an update

After this short premise let go analyze the GetToDoPage method:

        public static List<Tracker<ToDoView>> GetToDoPage(int pageDim, out int totalPages, int page = 1) 
        {
            List<Tracker<ToDoView>> result;
            using (SiteDbEntities context = new SiteDbEntities())
            {
                int rowCount = context.ToDo.Count();
                if (rowCount == 0)
                {
                    totalPages=0;
                    return new List<Tracker<ToDoView>>();
                }
                totalPages = rowCount / pageDim;
                if (rowCount % pageDim > 0) totalPages++;
                int toSkip = (page-1) * pageDim;
                result = (from item in context.ToDo
                          orderby item.DueDate ascending
                          select new Tracker<ToDoView>()
                          {
                           Value = new ToDoView() { Name = item.Name, Description = item.Description, DueDate = item.DueDate, id = item.id },
                           OldValue = new ToDoView() { Name = item.Name, Description = item.Description, DueDate = item.DueDate, id=item.id }, 
                          Changed=false }).Skip(toSkip).Take(pageDim).ToList();
            }
            return result;
        }

The result is of type  List<Tracker<ToDoView>> since we have used our wrapper around each data item. We create a context, with the using keyword to be sure it will be disposed at the end of the operation since it contains a connection to the database that is not a managed object.

As first operation we counts the total rows, then we do some mathematics to compute the pages: the remainder operation % is needed to take into account partially filled pages.In order to reach the request page we use the Skip and Take methods. In the select construct we create also our wrapper and fill it with two copies of the same data item, that will become the previous and actual version of the data item. Please notice also that we transfer data from the ToDo object into a fresh ToDoView object.

The UpdatePage method is a little bit more complex, but quite easy, too:

        public static void UpdatePage(List<Tracker<ToDoView>> items)
        {
            using (SiteDbEntities context = new SiteDbEntities())
            {
                bool aChange = false;
                foreach (Tracker<ToDoView> item in items)
                {
                    if (item.Changed)
                    {
                        if (item.OldValue == null) //insertion
                        {
                            if (item.Value != null)
                            {
                                ToDo curr=new ToDo() 
                                         { Name = item.Value.Name, Description = item.Value.Description, DueDate = item.Value.DueDate };
                                aChange = true;
                                context.ToDo.AddObject(curr);
                            }
                        }
                        else if (item.Value == null) //deletion
                        {
                            ToDo curr=new ToDo() { Name = item.OldValue.Name, Description = item.OldValue.Description, DueDate = item.OldValue.DueDate, id=item.OldValue.id.Value };
                            context.ToDo.Attach(curr);
                            context.ObjectStateManager.ChangeObjectState(curr, System.Data.EntityState.Deleted);
                            aChange = true;
                        }
                        else//update
                        {
                            ToDo curr = new ToDo() { Name = item.Value.Name, Description = item.Value.Description, DueDate = item.Value.DueDate, id=item.Value.id.Value };
                            context.ToDo.Attach(curr);
                            context.ObjectStateManager.ChangeObjectState(curr, System.Data.EntityState.Modified);
                            aChange = true;
                        }
                    }
                }
                if (aChange)
                {
                    try
                    {
                        context.SaveChanges();
                        items.ForEach((item) => { item.Confirm(); });//confirm changes have been passed
                    }
                    catch
                    {
                    }
                }
            }
        }
                    

We have a loop an all modified items where we verify if the item has changed, and if changed we analyze what operation needs to be done on the database, as previously.explained. Please notice the use of the ObjectStateManger to set the correct state of the various objects in the different cases.  The case of the insertion is the only one that doesn’t require to set manually the state of the object.

If at least a data item has changed we do a SubmitChanges() that passes all changes in a single transaction to the database. In  case no exception is fired we call the Confirm() method of the Tracker<T> wrapper  that sets the old version equal to the new version of the data item since all changes has been passed to the database.In case of exceptions an error message should be returned to the controller that need to say to the user to retry the post in a few minutes….however we have not handled this for sake of simplicity(a too complex example doesn’t help the understanding).

Now we can go now to the controller that has just two Action methods, one for handling the initial get and the second for handling the subsequent posts:       

         public const int PageDim=5;//into an actual application this should be put in a config file
        public ActionResult Index()
        {
            int totalPages;
            ToDoViewModel result = new ToDoViewModel()
                {
                    ToDoList = ToDoViewModel.GetToDoPage(PageDim, out totalPages),
                    TotalPages = totalPages,
                    CurrPage=1,
                    PrevPage=1
                };
            return View(result);
        }

        [HttpPost]     
        public ActionResult Index(ToDoViewModel model)
        {
            if (!ModelState.IsValid)
            {
                
                model.CurrPage=model.PrevPage; //cancel possible page change and force correcting errors
                return View(model);
            }
            else
            {
                ToDoViewModel.UpdatePage(model.ToDoList);
                int totalPages;
                ToDoViewModel result = new ToDoViewModel()
                {
                    ToDoList = ToDoViewModel.GetToDoPage(PageDim, out totalPages, model.CurrPage),
                    TotalPages = totalPages,
                    CurrPage = model.CurrPage,
                    PrevPage = model.CurrPage
                };
                return View(result);
            }
        }

 

The first method just displays the first page and it is quite trivial. The second method just controls if there are validation errors. In case there are it cancels a possible page change by resetting the current page to the previous page, and then returns the same View Model it received in order to let the user correct the errors. In case everything is ok it passes the changes to the database, and retrieve the new page requested by the user. That’s all!

We finally arrived to the datagrid. In order to have the datagrid working we need to prepare 4 templates:

  1. ToDoGrid: it displays the general container where all data items will be inserted. In our case it is just a table.
  2. ToDoDisplayItem: it displays a row of data when the grid is in display mode
  3. ToDoEditItem: it displays a row of data when the grid is in edit mode
  4. ToDoInsertItem: it defines the look of the insert new row component, normally it just displays an insert button.

Well, Let go see in detail each single template.

ToDoGrid
<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<Mvc_Examples.Models.ToDoView>" %>

<table class="ToDo" >

<tr>
<td class="ToDoHeader"><strong>Name</strong></td>
<td class="ToDoHeader"><strong>Due Date</strong></td>
<td class="ToDoHeader"><strong>Description</strong></td>
<td class="ToDoHeader"><strong></strong></td>
<td class="ToDoHeader"><strong></strong></td>
</tr>
<%:ViewData["Content"] as MvcHtmlString %>
</table>

It just displays the <table> tags and the header of the table. The <%:ViewData["Content"] as MvcHtmlString %> construct defines where all data items have to be inserted. It is a kind of placeholder and it needs to be inserted “as it is” in any template that describes a datagrid container.

It is worth to point out that this template is passed an empty data item object to help the automatic construction of the container. Specifically, we can use reflection to extract all columns and we can also automatically decide some facts about the look of the container by extracting the attributes of each data item property (as for instance the display attribute).

ToDoDisplayItem
          <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<Mvc_Examples.Models.ToDoView>" %>
          <%@ Import Namespace=" MVCControlsToolkit.Core" %>
          <%@ Import Namespace=" MVCControlsToolkit.Controls" %>
          
                      <td class="ToDo">
                          <%: Html.ValidationMessageFor(m => m.Name, "*")%><%: Model.Name %>
                      </td>
                      <td class="editor-field">
                          <%: Html.ValidationMessageFor(m => m.DueDate, "*")%><%: Model.DueDate.ToString("D")%>
                      </td>
                      <td class="ToDo">
                          <%: Html.ValidationMessageFor(m => m.Description, "*")%><%:  Model.Description %>
                      </td>
                      <td class="ToDoTool">
                          <%: Html.ImgDataButton(DataButtonType.Edit, "../../Content/edit.jpg", null)%>
                      </td>
                      <td class="ToDoTool">
                          <%: Html.ImgDataButton(DataButtonType.Delete, "../../Content/delete.jpg", null)%>

          The display item View Model is just a data item, it is not a Tracker<T> wrapper. The wrapper is handled automatically by the DataGrid.

          We don’t need to put the <tr> tag in each data item: the container tag for each item is defined in the DataGrid helper and it is automatically inserted by the DataGrid. We have also the option to supply a delegate that returns a different item container as a function of the data item and of its position in the DataGrid. 

          The last thing worth to discuss are the two data buttons: the first one switches the row in edit mode, while the second one just delete the row. I used here an image button but there are also link and normal buttons.

          ToDoEditItem
          <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<Mvc_Examples.Models.ToDoView>" %>
          <%@ Import Namespace=" MVCControlsToolkit.Core" %>
          <%@ Import Namespace=" MVCControlsToolkit.Controls" %>
                      
                      <td class="ToDo">
                          <%: Html.ValidationMessageFor(m => m.Name, "*")%><%: Html.TextBoxFor(m => m.Name) %>
                      </td>
                      <td class="ToDo">
                          <%: Html.ValidationMessageFor(m => m.DueDate, "*")%><%: Html.DateTimeFor(m => m.DueDate, DateTime.Today).Date()%>
                      </td>
                      <td class="ToDo">
                          <%: Html.ValidationMessageFor(m => m.Description, "*")%><%: Html.TextBoxFor(m => m.Description) %>
                      </td>
                      <td class="ToDoTool" colspan="2">
                          <%: Html.HiddenFor(m => m.id) %>
                          <%: Html.ImgDataButton(DataButtonType.Cancel, "../../Content/undo.jpg", null)%>
                      </td>

          The edit template is completely analogous to the display template. The only difference being that it contains input field to allow user to edit fields.

          Please, notice the Hidden filed containing the key! It is necessary! Here we have a cancel button that undo all changes done to the data item and put the row in display mode.

          Last thing worth to point out is the DateTimeFor helper that is able to take as input, date, time or date and time. It is able to read the DateRange attribute and to enforce its constraints. This means the user is allowed to insert only dates that conforms with the constraints. More information about the DateTimeFor Helper can be found here.

          ToDoInsertItem
          %@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<Mvc_Examples.Models.ToDoView>" %>
          <%@ Import Namespace=" MVCControlsToolkit.Core" %>
          <%@ Import Namespace=" MVCControlsToolkit.Controls" %>
          
          <td colspan="5" class="ToDo"><%: Html.ImgDataButton(DataButtonType.Insert, "../../Content/add.jpg", null)%></td>
          The insert template just contains an insert button that when clicked causes a new row to appear in edit mode.
          The Datagrid

          Once we have all templates defined we just need to use the datagrid and pager helpers:

          <div>
              <%:Html.DataGridFor(m => m.ToDoList, ItemContainerType.tr,  "ToDoEditItem",  "ToDoDisplayItem", "ToDoGrid", "ToDoInsertItem")%>
              </div>
              <div class="ToDoPager">
                              <% var pager = Html.PagerFor(m => m.CurrPage, m => m.PrevPage, m => m.TotalPages); %>
                              <%:pager.PageButton("<<", PageButtonType.First, PageButtonStyle.Link) %>
                              <%:pager.PageButton("<", PageButtonType.Previous, PageButtonStyle.Link) %>
                              <%:pager.PageChoice(5) %>
                              <%:pager.PageButton(">", PageButtonType.Next, PageButtonStyle.Link) %>
                              <%:pager.PageButton(">>", PageButtonType.Last, PageButtonStyle.Link) %>
                          </div>
              <div>
              <input type="submit" value="Save" />
              <%:Html.HiddenFor(m => m.TotalPages) %>

          The first argument of the helper is the definition of the property to display in the DataGrid, as usual, the second defines the item container, and the last ones are the names of the templates defined before.

          There are also optional arguments to define html attributes(also as a function of the data item) and to pass a function to change dynamically the item container.

          The pager is composed of various parts that can be also used separately. Here I used link buttons but one can use also image or normal buttons.

          Well we have finished this short adventure,,,,

          Next post will be about the new features of the new release of the datagrid:, sorting, master-detail helpers…….

                                                                  Stay Tuned !

                                                                  Francesco

          For more information or consulences feel free to contact me

          Tags: , , , , , ,