You can use delegates whenever you can use events. I'm not considering the cases where you're already bound to use events because of the library you use.
So, why using events at all? They essentially do what an delegate instance can do but introduce a number of limitations. It makes programming safer. In particular, the event can only be fired in the class where it is declared. For that reason events are used for event-oriented UI and represent Windows messages, for example.
Delegate is more basic concept than the event. Whenever you work with event (add a handler to it), a delegate instance is involved, but the delegates can be used without events.
Warning! One typical misconception is that events are multicast while delegates are not. This is not true. A delegates instance becomes multicast as soon as more than one event handler is added to its invocation list. Another misconception is that events require limitation of using
System.EventArguments and derived classes with
System.EvenHandler (generic or not). This is only a Microsoft recommendation, which I recommend to follow in all cases though. A failure to follow this recommendation is detected by FxCop but not compiler. There are no any special recommendations for delegates.
For more information, see
http://msdn.microsoft.com/en-us/library/17sde2xt.aspx[
^].
—SA
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