public void RemoveHandler(EventHandler <PropertyChangedEventArgs> handler, string propertyName)
{
PropertyRecord pr = (PropertyRecord)_dict[propertyName];
if (pr != null)
{
pr.RemoveHandler(handler);
if (pr.IsEmpty)
{
_dict.Remove(propertyName);
}
// invalidate list of all listeners
_dict.Remove(AllListenersKey);
_proposedAllListenersList = null;
}
}