using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DelegateDemo
{
    class Program
    {
        delegate void callBackdelegate(string strMessage);
        static void Main(string[] args)
        {
            callBackdelegate callback = ResultCallback;
            AddNumber(100, 200, callback);
            Console.ReadLine();
        }
        static void AddNumber(int num1, int num2,callBackdelegate callBack)
        {
            int result = num1 + num2;
            callBack("Result is : "+result.ToString());
        }
        static void ResultCallback(string strMessage)
        {
            Console.WriteLine(strMessage);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.Remoting.Messaging;

namespace DelegateDemo
{
    class Program
    {
        //声明一个委托，签名与AddNumber函数相同
        delegate int MethodDelegate(int num1, int num2);
        static void Main(string[] args)
        {
            MethodDelegate del = AddNumber;
            AsyncCallback callback = new AsyncCallback(ResultCallBack);

            IAsyncResult result = del.BeginInvoke(100, 200, callback, null);
            Console.WriteLine("UI线程继续执行。。。。");
            Console.ReadLine();
        }
        static int AddNumber(int num1, int num2)
        {
            //用线程模拟一个耗时的操作
            System.Threading.Thread.Sleep(5000);
            return num1 + num2;
        }
        static void ResultCallBack(IAsyncResult ar)
        {
            //将ar强制转换为 AsyncResult 类型 该类型需引入命名空间System.Runtime.Remoting.Messaging
            MethodDelegate del = (MethodDelegate)((AsyncResult)ar).AsyncDelegate;
            int result = del.EndInvoke(ar);
            Console.WriteLine("The result is :" + result.ToString());
        }
    }
}