using System;

 using System.Collections.Generic;

 using System.Linq;

 using System.Text;

 using System.Threading.Tasks;

 namespace WindowsFormsApplication1

 {

     public class delegateclass

     {

         private delegate int Dothread();

         static Dothread dothread = new Dothread(work);

         public static void start()

         {

             AsyncCallback backCall = new AsyncCallback(backcall);

             dothread.BeginInvoke(backCall, "我是异步调用的parameter");//第一个参数是调用work方法的参数，第二个是回调函数，第三个是需要传到回调函数里的参数可以是Object类型

         }

         /// <summary>

         ///这个是委托调用程序

         /// </summary>

         private static int work()

         {

             System.Windows.Forms.MessageBox.Show("我是委托调用程序");

             return ;

         }

         /// <summary>

         /// 回调函数

         /// </summary>

         /// <param name="parameter"></param>

         /// <returns></returns>

         private static int backcall(int parameter)

         {

             System.Windows.Forms.MessageBox.Show("这是一个回调函数");

             return ;

         }

         private static void backcall(IAsyncResult parameter)

         {

             int result=dothread.EndInvoke(parameter);

             System.Windows.Forms.MessageBox.Show("这是一个回调函数");

             System.Windows.Forms.MessageBox.Show(result.ToString());

             System.Windows.Forms.MessageBox.Show(parameter.AsyncState.ToString());

         }

     }

 }

 using System;

 using System.Collections.Generic;

 using System.ComponentModel;

 using System.Data;

 using System.Drawing;

 using System.Linq;

 using System.Text;

 using System.Threading.Tasks;

 using System.Windows.Forms;

 namespace WindowsFormsApplication1

 {

     public partial class Form1 : Form

     {

         public Form1()

         {

             InitializeComponent();

         }

         private void button1_Click(object sender, EventArgs e)

         {

             delegateclass.start();

         }

     }

 }