BaseObjectSpace.ModifiedChanging Event

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

Namespace: DevExpress.ExpressApp

Assembly: DevExpress.ExpressApp.v24.2.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.

File: MySolution.Blazor.Server/Startup.cs, MySolution.Win/Startup.cs, MySolution.WebApi/Startup.cs

C#

using DevExpress.ExpressApp;
// ...
builder.ObjectSpaceProviders.Events.OnObjectSpaceCreated = context => {
    var npos = context.ObjectSpace as NonPersistentObjectSpace;
    if (npos != null) {
        npos.ModifiedChanging += Npos_ModifiedChanging;
    }
};
// ...
private void Npos_ModifiedChanging(object sender, ObjectSpaceModificationEventArgs e) {
    if(e.MemberInfo!= null) {
        if(e.MemberInfo.Owner.Type == typeof(ProductView) && 
        e.MemberInfo.Name == nameof(ProductView.Category)) {
            e.Cancel = true;
        }
    }
}

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.

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