c# - Why can't I invoke PropertyChanged event from an Extension Method? -

i've tried code class avoid method "raisepropertychanged". know can inherit class has implementation in cases can't. i've tried extension method visual studio complain.

public static class extension {     public static void raisepropertychanged(this inotifypropertychanged predicate, string propertyname)     {         if (predicate.propertychanged != null)         {             predicate.propertychanged(propertyname, new propertychangedeventargs(propertyname));         }     } } 

it said:

"the event 'system.componentmodel.inotifypropertychanged.propertychanged' can appear on left hand side of += or -="

reed right. however, see you're trying (make code reusable—good you); , i'll point out rectified accepting propertychangedeventhandler delegate , passing within inotifypropertychanged implementation:

public static void raise(this propertychangedeventhandler handler, object sender, string propertyname) {     if (handler != null)     {         handler(sender, new propertychangedeventargs(propertyname));     } } 

then within class implements inotifypropertychanged, can call extension method so:

propertychanged.raise(this, "myproperty"); 

this works because, as marc said, within class declaring event can access field (which means can pass delegate argument method, including extension methods).