Question

I think I understand the concept of a delegate in C# as a pointer to a method, but I cant find any good examples of where it would be a good idea to use them. What are some examples that are either significantly more elegant/better with delegates or cant be solved using other methods?

Answer 1

What exactly do you mean by delegates? Here are two ways in which they can be used:

void Foo(Func<int, string> f) {  //do stuff  string s = f(42);  // do more stuff } 

and

void Bar() {  Func<int, string> f = delegate(i) { return i.ToString(); }  //do stuff  string s = f(42);  // do more stuff } 

The point in the second one is that you can declare new functions on the fly, as delegates. This can be largely replaced by lambda expressions,and is useful any time you have a small piece of logic you want to 1) pass to another function, or 2) just execute repeatedly. LINQ is a good example. Every LINQ function takes a lambda expression as its argument, specifying the behavior. For example, if you have a List<int> l then l.Select(x=>(x.ToString()) will call ToString() on every element in the list. And the lambda expression I wrote is implemented as a delegate.

The first case shows how Select might be implemented. You take a delegate as your argument, and then you call it when needed. This allows the caller to customize the behavior of the function. Taking Select() as an example again, the function itself guarantees that the delegate you pass to it will be called on every element in the list, and the output of each will be returned. What that delegate actually does is up to you. That makes it an amazingly flexible and general function.

Of course, they’re also used for subscribing to events. In a nutshell, delegates allow you to reference functions, using them as argument in function calls, assigning them to variables and whatever else you like to do.