How to use delegates?

See it.

A delegate is just such a type that you can write not * numbers and objects, but functions * to variables of this type, and call them later. That's all you need to know to begin with.

To declare such a variable, the compiler must know what type of arguments this function will have, and what type of return value. He needs this so that he knows how to correctly call a function on this variable, and what type the result will be. When you declare a delegate, you provide this information and:

delegate int mydel(int x, int y); ^ \_____________________/ | | объявляется делегат | | а это показывает, какие функции использовать с этим делегатом только вместо имени функции название делегата 

In your code, the function returns a value, so the return value must also be in the delegate definition.

You can fix the code like this:

 class Program { delegate int mydel(int x, int y); // поменяли возвращаемое значение на int static int sum(int x, int y) { return x + y; } static void Main(string[] args) { mydel g = sum; // здесь можно без new, просто присвоить. так проще, правда? int result = g(10, 5); Console.WriteLine("Sum = " + result); } } 

* ( Note to connoisseurs. ) Yes, this is a simplification. In fact, we have multicast delegate, so you can add and call them through Invoke / BeginInvoke . And yes, the delegate is an object. I simplify the picture for clarity.