/// <summary>
/// Adds a weak event listener for a CollectionChanged event.
/// </summary>
/// <param name="source">The source of the event.</param>
/// <param name="handler">The event handler.</param>
/// <exception cref="ArgumentNullException">source must not be <c>null</c>.</exception>
/// <exception cref="ArgumentNullException">handler must not be <c>null</c>.</exception>
protected void AddWeakEventListener( INotifyCollectionChanged source, NotifyCollectionChangedEventHandler handler )
{
if ( source == null )
throw new ArgumentNullException( "source" );
if ( handler == null )
throw new ArgumentNullException( "handler" );
CollectionChangedEventListener listener = collectionChangedListeners.LastOrDefault( ( l ) => l.Source == source && l.Handler == handler );
if ( listener == null )
listener = new CollectionChangedEventListener( source, handler );
else
return;
collectionChangedListeners.Add( listener );
CollectionChangedEventManager.AddListener( source, listener );
}
