How to: Perform CRUD Operations with Non-Persistent Objects

• Sep 24, 2019
• 5 minutes to read

This example demonstrates how to create, read, update and delete non-persistent objects. In this example, the static cache is used as a temporary storage for non-persistent objects.

1. Implement the following non-persistent class:

   C#

   using System;
   using System.ComponentModel;
   using DevExpress.ExpressApp;
   using DevExpress.ExpressApp.Data;
   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, "") {
       }
       [Key]
       public Int32 ID {
           get { return id; }
           set { id = value; }
       }
       public String Name {
           get { return name; }
           set {
               if (name != value) {
                   name = value;
                   RaisePropertyChanged(nameof(Name));
               }
           }
       }
       public event PropertyChangedEventHandler PropertyChanged;
       [Browsable(false)]
       public IObjectSpace ObjectSpace {
           get { return objectSpace; }
           set { objectSpace = value; }
       }
   }
   

   VB.NET

   Imports DevExpress.ExpressApp
   Imports DevExpress.ExpressApp.Data
   Imports DevExpress.ExpressApp.DC
   Imports DevExpress.Persistent.Base
   Imports System.ComponentModel
   ' ...
   <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
       <Key>
       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(NameOf(Name))
               End If
           End Set
       End Property
       Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
       <Browsable(False)>
       Public Property ObjectSpace() As IObjectSpace Implements IObjectSpaceLink.ObjectSpace
           Get
               Return _objectSpace
           End Get
           Set(ByVal value As IObjectSpace)
               _objectSpace = value
           End Set
       End Property
   End Class
   

2. Open the WinApplication.cs (WinApplication.vb), WebApplication.cs (WebApplication.vb), and/or MobileApplication.cs (MobileApplication.vb) file in a C#/VB Editor. Ensure that the NonPersistentObjectSpaceProvider is registered in the overridden CreateDefaultObjectSpaceProvider method (in addition to the existing XPObjectSpaceProvider or EFObjectSpaceProvider). The Solution Wizard adds this code automatically. Note that this code may be missing if you created your project in an older XAF version.

   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
   

3. Implement the following Controller:

   C#

   using System;
   using System.Collections.Generic;
   using System.ComponentModel;
   using DevExpress.ExpressApp;
   // ...
   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 NonPersistentObjectSpace_ObjectsGetting(Object sender, ObjectsGettingEventArgs e) {
           if (e.ObjectType == typeof(NonPersistentClass)) {
               IObjectSpace objectSpace = (IObjectSpace)sender;
               BindingList<NonPersistentClass> objects = new BindingList<NonPersistentClass>();
               objects.AllowNew = true;
               objects.AllowEdit = true;
               objects.AllowRemove = true;
               foreach (NonPersistentClass obj in objectsCache) {
                   objects.Add(objectSpace.GetObject<NonPersistentClass>(obj));
               }
               e.Objects = objects;
           }
       }
       private void NonPersistentObjectSpace_ObjectByKeyGetting(object sender, ObjectByKeyGettingEventArgs e) {
           IObjectSpace objectSpace = (IObjectSpace)sender;
           foreach (Object obj in objectsCache) {
               if (obj.GetType() == e.ObjectType && Equals(objectSpace.GetKeyValue(obj), e.Key)) {
                   e.Object = objectSpace.GetObject(obj);
                   break;
               }
           }
       }
       private void NonPersistentObjectSpace_ObjectGetting(object sender, ObjectGettingEventArgs e) {
           if (e.SourceObject is IObjectSpaceLink) {
               ((IObjectSpaceLink)e.TargetObject).ObjectSpace = (IObjectSpace)sender;
           }
       }
       private void NonPersistentObjectSpace_Committing(Object sender, CancelEventArgs e) {
           IObjectSpace objectSpace = (IObjectSpace)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_ObjectSpaceCreated(object sender, ObjectSpaceCreatedEventArgs e) {
           if (e.ObjectSpace is NonPersistentObjectSpace nonPersistentObjectSpace) {
               nonPersistentObjectSpace.ObjectsGetting += NonPersistentObjectSpace_ObjectsGetting;
               nonPersistentObjectSpace.ObjectByKeyGetting += NonPersistentObjectSpace_ObjectByKeyGetting;
               nonPersistentObjectSpace.ObjectGetting += NonPersistentObjectSpace_ObjectGetting;
               nonPersistentObjectSpace.Committing += NonPersistentObjectSpace_Committing;
           }
       }
       protected override void OnActivated() {
           base.OnActivated();
           Application.ObjectSpaceCreated += Application_ObjectSpaceCreated;
       }
       protected override void OnDeactivated() {
           base.OnDeactivated();
           Application.ObjectSpaceCreated -= Application_ObjectSpaceCreated;
       }
       public NonPersistentClassWindowController()
            : base() {
           TargetWindowType = WindowType.Main;
       }
   }
   

   VB.NET

   Imports DevExpress.ExpressApp
   Imports System.Collections.Generic
   Imports System.ComponentModel
   ' ...
   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 NonPersistentObjectSpace_ObjectsGetting(ByVal sender As Object, ByVal e As ObjectsGettingEventArgs)
           If e.ObjectType Is GetType(NonPersistentClass) Then
               Dim objectSpace As IObjectSpace = DirectCast(sender, IObjectSpace)
               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(objectSpace.GetObject(Of NonPersistentClass)(obj))
               Next obj
               e.Objects = objects
           End If
       End Sub
       Private Sub NonPersistentObjectSpace_ObjectByKeyGetting(ByVal sender As Object, ByVal e As ObjectByKeyGettingEventArgs)
           Dim objectSpace As IObjectSpace = DirectCast(sender, IObjectSpace)
           For Each obj As Object In objectsCache
               If obj.GetType() Is e.ObjectType AndAlso Equals(objectSpace.GetKeyValue(obj), e.Key) Then
                   e.Object = objectSpace.GetObject(obj)
                   Exit For
               End If
           Next obj
       End Sub
       Private Sub NonPersistentObjectSpace_ObjectGetting(ByVal sender As Object, ByVal e As ObjectGettingEventArgs)
           If TypeOf e.SourceObject Is IObjectSpaceLink Then
               DirectCast(e.TargetObject, IObjectSpaceLink).ObjectSpace = DirectCast(sender, IObjectSpace)
           End If
       End Sub
       Private Sub NonPersistentObjectSpace_Committing(ByVal sender As Object, ByVal e As CancelEventArgs)
           Dim objectSpace As IObjectSpace = DirectCast(sender, IObjectSpace)
           For Each obj As Object In objectSpace.ModifiedObjects
               If TypeOf obj Is NonPersistentClass Then
                   If objectSpace.IsNewObject(obj) Then
                       objectsCache.Add(DirectCast(obj, NonPersistentClass))
                   ElseIf objectSpace.IsDeletedObject(obj) Then
                       objectsCache.Remove(DirectCast(obj, NonPersistentClass))
                   End If
               End If
           Next obj
       End Sub
       Private Sub Application_ObjectSpaceCreated(ByVal sender As Object, ByVal e As ObjectSpaceCreatedEventArgs)
           If TypeOf e.ObjectSpace Is NonPersistentObjectSpace Then
               Dim nonPersistentObjectSpace As NonPersistentObjectSpace = CType(e.ObjectSpace, NonPersistentObjectSpace)
               AddHandler nonPersistentObjectSpace.ObjectsGetting, AddressOf NonPersistentObjectSpace_ObjectsGetting
               AddHandler nonPersistentObjectSpace.ObjectByKeyGetting, AddressOf NonPersistentObjectSpace_ObjectByKeyGetting
               AddHandler nonPersistentObjectSpace.ObjectGetting, AddressOf NonPersistentObjectSpace_ObjectGetting
               AddHandler nonPersistentObjectSpace.Committing, AddressOf NonPersistentObjectSpace_Committing
           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()
           MyBase.New()
           TargetWindowType = WindowType.Main
       End Sub
   End Class
   

   This Controller handles the following events:

   • NonPersistentObjectSpace.ObjectsGetting and NonPersistentObjectSpace.ObjectByKeyGetting - to provide objects the UI requests;
   • BaseObjectSpace.Committing - to store the Create and Delete operations’ result in memory;
   • NonPersistentObjectSpace.ObjectGetting - to change the IObjectSpaceLink.ObjectSpace property when an object is transferred between Object Spaces.