Understanding and Applying C# Delegates

What is a Delegate in C#?

A delegate in C# is a type that defines a method signature. It can be used to pass methods as arguments to other methods, to allow them to call the referenced methods or execute them asynchronously. Delegates are especially useful when creating events and callbacks.

Delegates are similar to C++ function pointers, but are type safe and are managed by the CLR. Delegates make it easier to program events, such as button clicks, without having to write a lot of procedural code.

Why Use Delegates in C#?

Delegates are often used in scenarios where it makes sense to pass around a method that needs to be called at some point in the future. For example, you might create a generic delegate that gets triggered whenever a certain event occurs. It's then up to each class that implements the delegate to respond accordingly.

Delegates also come in handy when implementing callback routines, where you want to be notified when certain events occur. By defining a delegate you can easily register a callback that's triggered whenever the identified event occurs.

Declaring a Delegate in C#

The simplest way to declare a delegate in C# is to use the delegate keyword followed by a method signature. Here’s an example:

public delegate void MyDel();

This defines a delegate that can point to any method that has no parameters and returns void.

Example of Using Delegates in C#

Let’s look at a more concrete example of using delegates in C#. Suppose we want to write a program that can be used to invoke a list of functions. The program should take the list of functions as an argument. We could do this using delegates as follows:

public delegate void MyDelegate(string s);

To invoke the delegates, we would call the following method:

public static void InvokeDelegates(List<MyDelegate> delegates) {     foreach (MyDelegate d in delegates)     {         d("Hello");     } }

In this example, we have declared a delegate that takes a string as a parameter and returns void. We then define a method that takes a list of this type of delegate and calls each one with the string “Hello”. In this way, we can invoke a list of functions with a single call.