Pattern for implementing INotifyPropertyChanged?

Question

I have seen the following pattern used for implementing INotifyPropertyChanged

private void NotifyPropertyChanged(string propertyName)
{
    PropertyChangedEvent         


        

Answer 1

Eric Lippert explains this in details in this blog article: Events and races.

Basically, the idea is to avoid a race condition in case another thread unsubscribes the last handler for this event after you check PropertyChanged != null, but before you actually invoke PropertyChanged. If you make a local copy of the handler, this cannot happen (but you might end up calling a handler that's just been unsubscribed)