How to: Display a Non-Persistent Object's Detail View from the Navigation

• Jul 05, 2019
• 4 minutes to read

This example demonstrates how to display a non-persistent object‘s Detail View from the Navigation, or as a Dashboard item.

Tip

If you wish to show a non-persistent object in a modal dialog window (e.g., your task is to ask a user to fill a form), then implement a PopupWindowShowAction Action, handle its PopupWindowShowAction.CustomizePopupWindowParams event and assign the required Detail View to the handler’s CustomizePopupWindowParamsEventArgs.View parameter. You can also use the ActionAttribute to show a non-persistent object by clicking an Action (see the Create an Action that Displays the Pop-up Dialog section of the How to: Create an Action Using the Action Attribute topic).

Show a Predefined Non-Persistent Object Instance

• Declare a non-persistent class decorated with the DomainComponentAttribute. Add an object key property decorated with the KeyAttribute.

  C#

  using DevExpress.ExpressApp.DC;
  // ...
  [DomainComponent]
  public class NonPersistentObject {
      [Browsable(false)]
      [DevExpress.ExpressApp.Data.Key]
      public int Oid { get; set; }
      public string Name { get; set; }
  }
  

  VB.NET

  Imports DevExpress.ExpressApp.DC
  ' ...
  <DomainComponent> _
  Public Class NonPersistentObject
      <Browsable(False), DevExpress.ExpressApp.Data.Key> _
      Public Property Oid() As Integer
      Public Property Name() As String
  End Class
  

  Note

  The INotifyPropertyChanged, IXafEntityObject and IObjectSpaceLink interface implementations were omitted in this example. However, it is recommended to support these interfaces in real-world applications (see PropertyChanged Event in Business Classes and Non-Persistent Objects).

• Rebuild the solution.

• Run the Model Editor for the module project and add an item to the navigation. Note that only the Default navigation group content is visible in Mobile applications. Set the IModelNavigationItem.View to the identifier of the DetailView to be displayed (e.g., NonPersistentObject_DetailView). Set the IModelNavigationItem.ObjectKey to an arbitrary integer value (this value should be unique if you are going to display several different non-persistent objects of this type).

  

  Note

  Similarly, you can create a dashboard item instead of the navigation item.

• Open the WinApplication.cs (WinApplication.vb) and/or WebApplication.cs (WebApplication.vb) code. Ensure that the NonPersistentObjectSpaceProvider is registered in the overridden CreateDefaultObjectSpaceProvider method (in addition to the existing XPObjectSpaceProvider or EFObjectSpaceProvider). Currently, this code is added automatically by the Solution Wizard, but it may be missing if you have created your project using an older version of XAF.

  C#

  protected override void CreateDefaultObjectSpaceProvider(CreateCustomObjectSpaceProviderEventArgs args) {
      // ...
      args.ObjectSpaceProviders.Add(new NonPersistentObjectSpaceProvider(TypesInfo, null));
  }
  

  VB.NET

  Protected Overrides Sub CreateDefaultObjectSpaceProvider(ByVal args As CreateCustomObjectSpaceProviderEventArgs)
      ' ...
      args.ObjectSpaceProviders.Add(New NonPersistentObjectSpaceProvider(TypesInfo, Nothing))
  End Sub
  

• Create a WindowController descendant and handle the NonPersistentObjectSpace.ObjectByKeyGetting event to get an instance of the object by a key specified in the previous step.

  C#

  using DevExpress.ExpressApp;
  // ...
  public class NonPersistentObjectsController : WindowController {
      private void Application_ObjectSpaceCreated(object sender, ObjectSpaceCreatedEventArgs e) {
          NonPersistentObjectSpace nonPersistentObjectSpace = e.ObjectSpace as NonPersistentObjectSpace;
          if(nonPersistentObjectSpace != null) {
              nonPersistentObjectSpace.ObjectByKeyGetting += nonPersistentObjectSpace_ObjectByKeyGetting;
          }
      }
      private void nonPersistentObjectSpace_ObjectByKeyGetting(object sender, ObjectByKeyGettingEventArgs e) {
          if(e.ObjectType.IsAssignableFrom(typeof(NonPersistentObject))) {
              if(((int)e.Key) == 138) {
                  NonPersistentObject obj138 = new NonPersistentObject();
                  obj138.Name = "Sample Object";
                  e.Object = obj138;
              }
          }
      }
      protected override void OnActivated() {
          base.OnActivated();
          Application.ObjectSpaceCreated += Application_ObjectSpaceCreated;
      }
      protected override void OnDeactivated() {
          base.OnDeactivated();
          Application.ObjectSpaceCreated -= Application_ObjectSpaceCreated;
      }
      public NonPersistentObjectsController() {
          TargetWindowType = WindowType.Main;
      }
  }
  

  VB.NET

  Imports Microsoft.VisualBasic
  Imports DevExpress.ExpressApp
  ' ...
  Public Class NonPersistentObjectsController
      Inherits WindowController
  
      Private Sub Application_ObjectSpaceCreated(ByVal sender As Object, ByVal e As ObjectSpaceCreatedEventArgs)
          Dim nonPersistentObjectSpace As NonPersistentObjectSpace = TryCast(e.ObjectSpace, NonPersistentObjectSpace)
          If nonPersistentObjectSpace IsNot Nothing Then
              AddHandler nonPersistentObjectSpace.ObjectByKeyGetting, AddressOf nonPersistentObjectSpace_ObjectByKeyGetting
          End If
      End Sub
      Private Sub nonPersistentObjectSpace_ObjectByKeyGetting(ByVal sender As Object, ByVal e As ObjectByKeyGettingEventArgs)
          If e.ObjectType.IsAssignableFrom(GetType(NonPersistentObject)) Then
              If (CInt(Fix(e.Key))) = 138 Then
                  Dim obj138 As New NonPersistentObject()
                  obj138.Name = "Sample Object"
                  e.Object = obj138
              End If
          End If
      End Sub
      Protected Overrides Sub OnActivated()
          MyBase.OnActivated()
          AddHandler Application.ObjectSpaceCreated, AddressOf Application_ObjectSpaceCreated
      End Sub
      Protected Overrides Sub OnDeactivated()
          MyBase.OnDeactivated()
          RemoveHandler Application.ObjectSpaceCreated, AddressOf Application_ObjectSpaceCreated
      End Sub
      Public Sub New()
          TargetWindowType = WindowType.Main
      End Sub
  End Class
  

Show a New Non-Persistent Object

If you want to create a non-persistent object automatically for each Detail View, you do not need to specify an ObjectKey in the Model Editor. Leave the ObjectKey value empty and create the following View Controller, which will create a non-persistent object automatically.

C#

using DevExpress.ExpressApp;
// ...
public class NonPersistentObjectActivatorController : ObjectViewController<DetailView, NonPersistentObject> {
    protected override void OnActivated() {
        base.OnActivated();
        if ((ObjectSpace is NonPersistentObjectSpace) && (View.CurrentObject == null)) {
            View.CurrentObject = View.ObjectTypeInfo.CreateInstance();
            View.ViewEditMode = DevExpress.ExpressApp.Editors.ViewEditMode.Edit;
        }
    }
}

VB.NET

Imports DevExpress.ExpressApp
' ...
Public Class NonPersistentObjectActivatorController
    Inherits ObjectViewController(Of DetailView, NonPersistentObject)

    Protected Overrides Sub OnActivated()
        MyBase.OnActivated()
        If (TypeOf ObjectSpace Is NonPersistentObjectSpace) AndAlso (View.CurrentObject Is Nothing) Then
            View.CurrentObject = View.ObjectTypeInfo.CreateInstance()
            View.ViewEditMode = DevExpress.ExpressApp.Editors.ViewEditMode.Edit
        End If
    End Sub
End Class

The object will be instantiated using its default constructor. You can also pass arguments to the CreateInstance method to use another constructor.