Delegates in C#

using System;

namespace NilPointer
{
    class Program
    {
        public delegate double CalCulate(double a, double b);

        public static double Add(double a, double b)
        {
            return a + b;
        }

        public static double Sub(double a, double b)
        {
            return a - b;
        }

        public static double Mul(double a, double b)
        {
            return a * b;
        }

        static void Main(string[] args)
        {
            CalCulate calCulate = Add;
            Console.WriteLine("Add: " + calCulate(1, 2));

            calCulate = Sub;
            Console.WriteLine("Sub: " + calCulate(10, 2));

            calCulate = Mul;
            Console.WriteLine("Mul: " + calCulate(10, 2));

            Console.ReadLine();
        }
    }
}

Output

Add: 3
Sub: 8
Mul: 20