Observer pattern implemented in C# with delegates?

Question

There is a question already answered which is http://stackoverflow.com/questions/32034/in-c-isnt-the-observer-pattern-already-implemented-using-events

It asks if the observer pattern is already implemented in c# using events.

While I get the events and observer pattern, isn't the observer pattern really just delegates and events is a further implementation?

Answer 1

You are correct. An event is simply a delegate with some slightly different functionality. All of the observer pattern can be implemented with delegates without ever touching the event keyword.

You may be interested then, in what the "event" keyword actually brings to the table.

• Events can be part of an interface, whereas regular delegate field cannot
• Events cannot be invoked by outside classes, but regular delegates can
• Events have additional accessors (add and remove) that you can override and provide custom functionality for

Edit: Here's a great writeup with IL code comparison between events and delegates. (Hint: it's pretty much the same).