The Notification method is called when the object specified by the Item parameter is being destroyed.
Do not call the Notification method in an application. Notification is called automatically when the collection item specified by Item is about to be deleted.
A collection item can, if needed, act on the notification that a collection item is being removed. For example, if a collection has object fields or properties that contain references to other collection items, it can check the notifications of collection item removals and invalidate those references as needed.