public void AddNotifyCollectionChangedHandler(object value, IHandleNotifyCollectionChanged handler)
{
RemoveNotifyCollectionChangedHandler(value, handler);
var notifyCollectionChanged = value as INotifyCollectionChanged;
if (notifyCollectionChanged != null && handler != null)
{
notifyCollectionChanged.CollectionChanged += handler.HandleNotifyCollectionChanged;
}
}