protected void AddEventListener(INotifyCollectionChanged source, NotifyCollectionChangedEventHandler handler)
{
if (source == null) { throw new ArgumentException("source"); }
if (handler == null) { throw new ArgumentException("handler"); }
CollectionChangedEventListener listener = new CollectionChangedEventListener(source, handler);
collectionEventListeners.Add(listener);
CollectionChangedEventManager.AddListener(source, listener);
}