If you don’t already know…

A delegate is a type that references a method. Once a delegate is assigned a method, it behaves exactly like that method. The delegate method can be used like any other method, with parameters and a return value… ~ MSDN
If you still don’t get it, I’ll break it down even more…

In Depth Look

A delegate is someone (or something) designated to act for or represent someone (or something) else. When coding, a delegate represents a defined method. A great example for using delegates is a simple calculator.

Calculator Scenario

Say you want to perform an operation on two numbers, x and y. That operation can be addition, subtraction, multiplication or division. The parameters are the same no matter which type of calculation you want to perform.

The only difference in the above code is the operator that’s used. That being the case, what if we could call one method and pass in a parameter telling us which operator to use? That’s where delegates come into play.

Delegates represent Methods

Let’s define a delegate and the methods that it will represent:

As you can see, the method definitions and the delegate method look the same except for the delegate keyword in front of the return type. Think of the delegate method as a template of the type of method in which it can call. For instance, a delegate method with a return type of string can only represent a method with the return type of string. Also notice that the delegate method looks like a normal method except that it has no method body. That’s because it’s going to call the body of the method that it’s referencing. But how does a delegate know which method to call?

Calling all methods!

You have to decide which method the delegate will call by assigning that method to the delegate. Let’s say I want to call the Add() method. Let’s instantiate a delegate variable:

The delegate variable calculate now represents the Add() method. So now when you call:

the variable result will equal 8.

Why not just call the Add() method!?!

Well, you could. This is what I was thinking, at first, until I realized that delegates are very powerful, especially when used as a Callback or with Anonymous Methods. But I’ll save that for another article.

Happy Coding!