Why do we need C# delegates

Question

I never seem to understand why we need delegates? I know they are immutable reference types that hold reference of a method but why can't we just call the method directly, instead of calling it via a delegate?

Thanks

Answer 1

Simple answer: the code needing to perform the action doesn't know the method to call when it's written. You can only call the method directly if you know at compile-time which method to call, right? So if you want to abstract out the idea of "perform action X at the appropriate time" you need some representation of the action, so that the method calling the action doesn't need to know the exact implementation ahead of time.

For example:

• Enumerable.Select in LINQ can't know the projection you want to use unless you tell it
• The author of Button didn't know what you want the action to be when the user clicks on it
• If a new Thread only ever did one thing, it would be pretty boring...

It may help you to think of delegates as being like single-method interfaces, but with a lot of language syntax to make them easy to use, and funky support for asynchronous execution and multicasting.