expressappframework-devexpress-dot-expressapp-dot-baseobjectspace-a332dddf.md
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.v25.2.dll
NuGet Package : DevExpress.ExpressApp
public event EventHandler<ObjectSpaceModificationEventArgs> ModifiedChanging
Public Event ModifiedChanging As EventHandler(Of ObjectSpaceModificationEventArgs)
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 that had its value changed. Returns null if it is impossible to determine what property causes the change. Inherited from ObjectChangedEventArgs. |
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
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;
}
}
}
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.
objectSpace.Reloaded += ObjectSpace_Reloaded;
objectSpace.ModifiedChanging += ObjectSpace_ModifiedChanging;
}
See Also
How to edit a collection of Persistent Objects linked to a Non-Persistent Object