Question

When I run these 2 lines of code I get what I expect:

Func<int, int> sqr = x => x * x;
Console.WriteLine(sqr(3)); 

But I don’t understand why the return is specified as the 2nd argument? How does it all work? When you define a delegate it has to be:

return-type delegate delName (parameters);

However, with Func delegate, the return type is also specified as the input argument. Can anybody explain me how it all works? And if possible, write a small example using the same concept of specifying the return type as the input parameter. I find it very difficult to understand what is happening under the hood.

Thanks in advance 🙂

Answer 1

The full declaration for System.Func you’re talking about is

public delegate TResult Func<T, TResult>(T arg)

So when you do

Func<int, int> sqr = x => x * x;

You’re declaring a method using a lambda expression which takes an int x and returns x * x. So right now sqr is holding a reference to your method. And in the following line

Console.WriteLine(sqr(3)); 

You actually execute the method and show the output.