OperationDelegate

using System;
namespace DelegateSample1
{
    //define delegate
    public delegate int OperationDelegate(int x, int y);
    class Operator
    {
        private int _x, _y;
        static void Main(string[] args)
        {
            OperationDelegate del = null;
            del += new OperationDelegate(Plus);
            del += new OperationDelegate(Subtract);

            Operator op = new Operator(5, 3);
            op.Operate(del);//Execute two method

            //remove a delegate instance
            del -= new OperationDelegate(Subtract);
            op.Operate(del);
            Console.ReadLine();
        }

        public void Operate(OperationDelegate del)
        {
            int i = del(_x, _y);
        }

        public Operator(int x, int y)
        {
            this._x = x;
            this._y = y;
        }
        /// <summary>
        /// Plus
        /// </summary>
        /// <param name="x">x</param>
        /// <param name="y">y</param>
        /// <returns></returns>
        private static int Plus(int x, int y)
        {
            int result = x + y;
            Console.WriteLine("x + y = {0}", result);
            return result;
        }

        /// <summary>
        /// Subtract
        /// </summary>
        /// <param name="x">x</param>
        /// <param name="y">y</param>
        /// <returns></returns>
        private static int Subtract(int x, int y)
        {
            int result = x - y;
            Console.WriteLine("x - y = {0}", result);
            return result;
        }     

    }

}