How to: Perform CRUD Operations with Non-Persistent Objects

• Feb 24, 2022
• 5 minutes to read

This example demonstrates how you can create, read, update end delete (perform CRUD operations) with non-persistent objects. The static cache is used here as a temporary storage for non-persistent objects. However, you can implement any other storage that meets your requirements.

Note

Mobile applications do not support CRUD operations for non-persistent objects, so the approach described in this topic is not supported by the Mobile platform. If it is necessary to implement this scenario in your Mobile application, contact us using the Support Center.

• Implement the following non-persistent class.

  C#

  using DevExpress.ExpressApp;
  using DevExpress.ExpressApp.DC;
  using DevExpress.Persistent.Base;
  // ...
  [DomainComponent, DefaultClassOptions]
  public class NonPersistentClass : IObjectSpaceLink, INotifyPropertyChanged {
      private Int32 id;
      private String name;
      private IObjectSpace objectSpace;
      protected void RaisePropertyChanged(String propertyName) {
          if(PropertyChanged != null) {
              PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
          }
      }
      public NonPersistentClass(Int32 id, String name)
          : base() {
          this.id = id;
          this.name = name;
      }
      public NonPersistentClass()
          : this(0, "") {
      }
      public Int32 ID {
          get { return id; }
          set { id = value; }
      }
      public String Name {
          get { return name; }
          set {
              if(name != value) {
                  name = value;
                  RaisePropertyChanged("Name");
              }
          }
      }
      public event PropertyChangedEventHandler PropertyChanged;
      [Browsable(false)]
      public IObjectSpace ObjectSpace {
          get { return objectSpace; }
          set { objectSpace = value; }
      }
  }
  

  VB.NET

  Imports DevExpress.ExpressApp
  Imports DevExpress.ExpressApp.DC
  Imports DevExpress.Persistent.Base
  ' ...
  <DomainComponent, DefaultClassOptions> _
  Public Class NonPersistentClass
      Implements IObjectSpaceLink, INotifyPropertyChanged
      Private _id As Int32
      Private _name As String
      Private _objectSpace As IObjectSpace
      Protected Sub RaisePropertyChanged(ByVal propertyName As String)
          RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
      End Sub
      Public Sub New(ByVal id As Int32, ByVal name As String)
          MyBase.New()
          Me._id = id
          Me._name = name
      End Sub
      Public Sub New()
          Me.New(0, "")
      End Sub
      Public Property ID() As Int32
          Get
              Return _id
          End Get
          Set(ByVal value As Int32)
              _id = value
          End Set
      End Property
      Public Property Name() As String
          Get
              Return _name
          End Get
          Set(ByVal value As String)
              If _name <> value Then
                  _name = value
                  RaisePropertyChanged("Name")
              End If
          End Set
      End Property
      Public Event PropertyChanged As PropertyChangedEventHandler
      <Browsable(False)> _
      Public Property ObjectSpace() As IObjectSpace
          Get
              Return _objectSpace
          End Get
          Set(ByVal value As IObjectSpace)
              _objectSpace = value
          End Set
      End Property
  End Class
  

• 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
  

• The New, Delete and Save Actions are available for non-persistent objects. With the following Controller, you can access modified non-persistent objects using the NonPersistentObjectSpace.ModifiedObjects property.

  C#

  using DevExpress.ExpressApp;
  using System.Collections.Generic;
  // ...
  public class NonPersistentClassWindowController : WindowController {
      private static List<NonPersistentClass> objectsCache;
      static NonPersistentClassWindowController() {
          objectsCache = new List<NonPersistentClass>();
          objectsCache.Add(new NonPersistentClass(1, "A"));
          objectsCache.Add(new NonPersistentClass(2, "B"));
          objectsCache.Add(new NonPersistentClass(3, "C"));
          objectsCache.Add(new NonPersistentClass(4, "D"));
          objectsCache.Add(new NonPersistentClass(5, "E"));
      }
      private void ObjectSpace_ObjectsGetting(Object sender, ObjectsGettingEventArgs e) {
          BindingList<NonPersistentClass> objects = new BindingList<NonPersistentClass>();
          objects.AllowNew = true;
          objects.AllowEdit = true;
          objects.AllowRemove = true;
          foreach(NonPersistentClass obj in objectsCache) {
              objects.Add(obj);
          }
          e.Objects = objects;
      }
      private void ObjectSpace_Committing(Object sender, CancelEventArgs e) {
          NonPersistentObjectSpace objectSpace = (NonPersistentObjectSpace)sender;
          foreach(Object obj in objectSpace.ModifiedObjects) {
              if(obj is NonPersistentClass) {
                  if(objectSpace.IsNewObject(obj)) {
                      objectsCache.Add((NonPersistentClass)obj);
                  }
                  else if(objectSpace.IsDeletedObject(obj)) {
                      objectsCache.Remove((NonPersistentClass)obj);
                  }
              }
          }
      }
      private void Application_ViewCreated(Object sender, ViewCreatedEventArgs e) {
          ObjectView objectView = e.View as ObjectView;
          if((objectView != null) && (objectView.ObjectTypeInfo.Type == typeof(NonPersistentClass))) {
              objectView.ObjectSpace.Committing += ObjectSpace_Committing;
              if(objectView is ListView) {
                  ((NonPersistentObjectSpace)objectView.ObjectSpace).ObjectsGetting += ObjectSpace_ObjectsGetting;
                  ((ListView)objectView).CollectionSource.ResetCollection();
              }
          }
      }
      protected override void OnActivated() {
          base.OnActivated();
          Application.ViewCreated += Application_ViewCreated;
      }
      protected override void OnDeactivated() {
          base.OnDeactivated();
          Application.ViewCreated -= Application_ViewCreated;
      }
     public NonPersistentClassWindowController()
          : base() {
          TargetWindowType = WindowType.Main;
      }
  }
  

  VB.NET

  Imports DevExpress.ExpressApp
  Imports System.Collections.Generic
  ' ...
  Public Class NonPersistentClassWindowController
      Inherits WindowController
  
      Private Shared objectsCache As List(Of NonPersistentClass)
      Shared Sub New()
          objectsCache = New List(Of NonPersistentClass)()
          objectsCache.Add(New NonPersistentClass(1, "A"))
          objectsCache.Add(New NonPersistentClass(2, "B"))
          objectsCache.Add(New NonPersistentClass(3, "C"))
          objectsCache.Add(New NonPersistentClass(4, "D"))
          objectsCache.Add(New NonPersistentClass(5, "E"))
      End Sub
      Private Sub ObjectSpace_ObjectsGetting(ByVal sender As Object, ByVal e As ObjectsGettingEventArgs)
          Dim objects As New BindingList(Of NonPersistentClass)()
          objects.AllowNew = True
          objects.AllowEdit = True
          objects.AllowRemove = True
          For Each obj As NonPersistentClass In objectsCache
              objects.Add(obj)
          Next obj
          e.Objects = objects
      End Sub
      Private Sub ObjectSpace_Committing(ByVal sender As Object, ByVal e As CancelEventArgs)
          Dim objectSpace As NonPersistentObjectSpace = CType(sender, NonPersistentObjectSpace)
          For Each obj As Object In objectSpace.ModifiedObjects
              If TypeOf obj Is NonPersistentClass Then
                  If objectSpace.IsNewObject(obj) Then
                      objectsCache.Add(CType(obj, NonPersistentClass))
                  ElseIf objectSpace.IsDeletedObject(obj) Then
                      objectsCache.Remove(CType(obj, NonPersistentClass))
                  End If
              End If
          Next obj
      End Sub
      Private Sub Application_ViewCreated(ByVal sender As Object, ByVal e As ViewCreatedEventArgs)
          Dim objectView As ObjectView = TryCast(e.View, ObjectView)
          If (objectView IsNot Nothing) AndAlso (objectView.ObjectTypeInfo.Type Is GetType(NonPersistentClass)) Then
              AddHandler objectView.ObjectSpace.Committing, AddressOf ObjectSpace_Committing
              If TypeOf objectView Is ListView Then
                  AddHandler CType(objectView.ObjectSpace, NonPersistentObjectSpace).ObjectsGetting, _
                  AddressOf ObjectSpace_ObjectsGetting
                  CType(objectView, ListView).CollectionSource.ResetCollection()
              End If
          End If
      End Sub
      Protected Overrides Sub OnActivated()
          MyBase.OnActivated()
          AddHandler Application.ViewCreated, AddressOf Application_ViewCreated
      End Sub
      Protected Overrides Sub OnDeactivated()
          MyBase.OnDeactivated()
          RemoveHandler Application.ViewCreated, AddressOf Application_ViewCreated
      End Sub
     Public Sub New()
          MyBase.New()
          TargetWindowType = WindowType.Main
     End Sub
  End Class