Understand specific usage of delegate in C#

Question

According to the MSDN documentation, it says it's useful for following purposes in addition to others which are understandable:

A class may need more than one implementation of the method.
It is desirable to encapsulate a static method.

Can someone help me understand these usages with an example?

It's in the section When to Use Delegates Instead of Interfaces (C# Programming Guide https://msdn.microsoft.com/en-us/library/ms173173.aspx — venerik, Nov 07 '15 at 20:01

score 4 · Answer 1 · edited May 23 '17 at 12:15

A delegate is a reference to a method that you can pass around as an object.

Imagine how useful it could be to have a method that allows its callers to provide part of its own logic. Every caller can have their own method, create a delegate (reference) to their method, and pass it to the method as a parameter. As long as the main method knows what arguments to pass in (if any), it can invoke the method by its reference (delegate).

Here's a simple example, specifically of usage #1 in your question:

void RemoveItem(string item, Action preRemoveLogic)
{
   preRemoveLogic(); //we don't know what method this actually points to,
                     //but we can still call it.
   //remove the item
}

void MyCustomLogic()
{
   //do something cool
}

/* snip */
RemoveItem("the item", new Action(MyCustomLogic));
//I can pass a reference to a method! Neat!

Delegates are also very important for making events work in .NET.

Understand specific usage of delegate in C#

1 Answers1