BaseObjectSpace.ModifiedChanging Event

Occurs before the IsModified property is changed to true. Handle this event to cancel or force the IsModified property to change.

Namespace: DevExpress.ExpressApp

Assembly: DevExpress.ExpressApp.v23.2.dll

NuGet Package: DevExpress.ExpressApp

Declaration

C#

public event EventHandler<ObjectSpaceModificationEventArgs> ModifiedChanging

VB.NET

Public Event ModifiedChanging As EventHandler(Of ObjectSpaceModificationEventArgs)

Event Data

The ModifiedChanging event's data class is ObjectSpaceModificationEventArgs. The following properties provide information specific to this event:

Property	Description
Cancel	Specifies whether the IsModified property change must be canceled.
MemberInfo	Specifies an object that is information on the property whose value has been changed. Inherited from ObjectChangedEventArgs.
NewValue	Specifies the new value of a changed property. Inherited from ObjectChangedEventArgs.
Object	Provides access to the object that is being manipulated. Inherited from ObjectManipulatingEventArgs.
OldValue	Specifies the old value of a changed property. Inherited from ObjectChangedEventArgs.
PropertyName	Specifies the name of a property whose value has been changed. Returns null (Nothing in VB) if it is impossible to determine what property causes the change. Inherited from ObjectChangedEventArgs.

Remarks

The following example shows how to cancel the IsModified property change when you modify the Category property of a ProductView object. In this case, the current Object Space does not add this object to the ModifiedObjects collection.

C#

using System;
using DevExpress.ExpressApp;
// ...
public sealed partial class MySolutionModule : ModuleBase {
    // ...
    public override void Setup(XafApplication application) {
        base.Setup(application);
        application.SetupComplete += Application_SetupComplete;
    }
    private void Application_SetupComplete(object sender, EventArgs e) {
        Application.ObjectSpaceCreated += Application_ObjectSpaceCreated;
    }
    private void Application_ObjectSpaceCreated(object sender, ObjectSpaceCreatedEventArgs e) {
        var npos = e.ObjectSpace as NonPersistentObjectSpace;
        if(npos != null) {
            npos.ModifiedChanging += ObjectSpace_ModifiedChanging;
        }
    }
    private void ObjectSpace_ModifiedChanging(object sender, CancelObjectChangedEventArgs e) {
        if(e.MemberInfo!= null) {
            if(e.MemberInfo.Owner.Type == typeof(ProductView) && 
            e.MemberInfo.Name == nameof(ProductView.Category)) {
                e.Cancel = true;
            }
        }
    }
}

VB.NET

Imports System
Imports DevExpress.ExpressApp
' ...
Public NotInheritable Partial Class MySolutionModule
    Inherits ModuleBase
    ' ...
    Public Overrides Sub Setup(ByVal application As XafApplication)
        MyBase.Setup(application)
        AddHandler application.SetupComplete, AddressOf Application_SetupComplete
    End Sub
    Private Sub Application_SetupComplete(ByVal sender As Object, ByVal e As EventArgs)
        AddHandler Application.ObjectSpaceCreated, AddressOf Application_ObjectSpaceCreated
    End Sub
    Private Sub Application_ObjectSpaceCreated(ByVal sender As Object, ByVal e As ObjectSpaceCreatedEventArgs)
        Dim npos As NonPersistentObjectSpace = TryCast(e.ObjectSpace, NonPersistentObjectSpace)
        If npos IsNot Nothing Then
            AddHandler npos.ModifiedChanging, AddressOf ObjectSpace_ModifiedChanging
        End If
    End Sub
    Private Sub ObjectSpace_ModifiedChanging(ByVal sender As Object, ByVal e As CancelObjectChangedEventArgs)
        If e.MemberInfo IsNot Nothing Then
            If e.MemberInfo.Owner.Type Is GetType(ProductView) AndAlso 
            e.MemberInfo.Name = NameOf(ProductView.Category) Then
                e.Cancel = True
            End If
        End If
    End Sub
End Class

Related GitHub Examples

The following code snippet (auto-collected from DevExpress Examples) contains a reference to the ModifiedChanging event.

Note

The algorithm used to collect these code examples remains a work in progress. Accordingly, the links and snippets below may produce inaccurate results. If you encounter an issue with code examples below, please use the feedback form on this page to report the issue.

C#

XAF_Non-Persistent-Objects-Edit-Linked-Persistent-Objects-Demo/CS/NonPersistentObjectsDemo.Module/BusinessObjects/ProductView.cs#L64

    objectSpace.Reloaded += ObjectSpace_Reloaded;
    objectSpace.ModifiedChanging += ObjectSpace_ModifiedChanging;
}

VB.NET

XAF_Non-Persistent-Objects-Edit-Linked-Persistent-Objects-Demo/VB/NonPersistentObjectsDemo.Module/BusinessObjects/ProductView.vb#L67

    AddHandler objectSpace.Reloaded, AddressOf ObjectSpace_Reloaded
    AddHandler objectSpace.ModifiedChanging, AddressOf ObjectSpace_ModifiedChanging
End Sub