Microsoft Developer Network
 INotifyCollectionChanged Interface
.NET Framework Class Library
INotifyCollectionChanged Interface

Notifies listeners of dynamic changes, such as when items get added and removed or the whole list is refreshed.

Namespace:  System.Collections.Specialized
Assembly:  WindowsBase (in WindowsBase.dll)
Visual Basic (Declaration)
Public Interface INotifyCollectionChanged
Visual Basic (Usage)
Dim instance As INotifyCollectionChanged
C#
public interface INotifyCollectionChanged
Visual C++
public interface class INotifyCollectionChanged
JScript
public interface INotifyCollectionChanged
XAML
Interfaces cannot be used directly in XAML; see types that implement this interface.

You can enumerate over any collection that implements the IEnumerable interface. However, to set up dynamic bindings so that insertions or deletions in the collection update the UI automatically, the collection must implement the INotifyCollectionChanged interface. This interface exposes the CollectionChanged event that must be raised whenever the underlying collection changes.

WPF provides the ObservableCollection<(Of <(T>)>) class, which is a built-in implementation of a data collection that exposes the INotifyCollectionChanged interface. For an example, see How to: Create and Bind to an ObservableCollection.

The individual data objects within the collection must satisfy the requirements described in the Binding Sources Overview.

Before implementing your own collection, consider using ObservableCollection<(Of <(T>)>) or one of the existing collection classes, such as List<(Of <(T>)>), Collection<(Of <(T>)>), and BindingList<(Of <(T>)>), among many others.

If you have an advanced scenario and want to implement your own collection, consider using IList, which provides a non-generic collection of objects that can be individually accessed by index and provides the best performance.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0
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The ultimate observer      LukeSkywalker   |   Edit   |   Show History
In WPF and I assume Silverlight, the eventual observer of events in a class implementing this interface and wired-up to the UI directly, is a class called ItemContainerGenerator and in particular, its OnCollectionChanged methods.

Seemingly, the aforementioned class keeps a copy of the collection - in UIElements - and mimics changes seen in the observable collection.
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