C# 委托简单例子

public delegate double Delegate_Prod(int a,int b);
class Class1
{
    static double fn_Prodvalues(int val1,int val2)
    {
        return val1*val2;
    }
    static void Main(string[] args)
    {
        //Creating the Delegate Instance
        Delegate_Prod delObj = new Delegate_Prod(fn_Prodvalues);
        Console.Write("Please Enter Values");
        int v1 = Int32.Parse(Console.ReadLine());
        int v2 = Int32.Parse(Console.ReadLine());
        //use a delegate for processing
        double res = delObj(v1,v2);
        Console.WriteLine ("Result :"+res);
        Console.ReadLine();
    }
}

namespace ConsoleApplication
{
    //定义代理
    delegate String Mydelegate();
    class temp
    {
        static void Main(String[] args)
        {
            //实例化代理
            Mydelegate Md = new Mydelegate(AsyncMethod);
            //实例一个回调代理
            AsyncCallback callback = new AsyncCallback(callbackMethod);
            //开始执行异步方法
            Md.BeginInvoke(callback, Md);
            Console.ReadLine();
        }
        //异步调用的方法
        static String AsyncMethod()
        {
            Console.WriteLine("异步方法正执行");
            String str = "异步调用已结束";
            return str;
        }

        //回调方法
        static void callbackMethod(IAsyncResult Ias)
        {
            Mydelegate Md = (Mydelegate)Ias.AsyncState;
            String  str = Md.EndInvoke(Ias);
            Console.WriteLine(str);
        }
    }
}

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

using System.Threading;
using System.Runtime.Remoting.Messaging;

namespace ConsoleTest
{
    public delegate int AddHandler(int a,int b);
    public class 加法类
    {
        public static int Add(int a, int b)
        {
            Console.WriteLine("开始计算：" + a + "+" + b);
            Thread.Sleep(3000); //模拟该方法运行三秒
            Console.WriteLine("计算完成！");
            return a + b;
        }
    }

    public class 同步调用
    {
        static void Main()
        {
            Console.WriteLine("===== 同步调用 SyncInvokeTest =====");
            AddHandler handler = new AddHandler(加法类.Add);
            int result = handler.Invoke(1, 2);

            Console.WriteLine("继续做别的事情。。。");

            Console.WriteLine(result);
            Console.ReadKey();
        }
        
    }

    public class 异步调用
    {
        static void Main()
        {
            Console.WriteLine("===== 异步调用 AsyncInvokeTest =====");
            AddHandler handler = new AddHandler(加法类.Add);

            //IAsyncResult: 异步操作接口(interface)
            //BeginInvoke: 委托(delegate)的一个异步方法的开始
            IAsyncResult result = handler.BeginInvoke(1, 2, null, null);

            Console.WriteLine("继续做别的事情。。。");

            //异步操作返回
            Console.WriteLine(handler.EndInvoke(result));
            Console.ReadKey();
        }
        
    }

    public class 异步回调
    {
        static void Main()
        {
            Console.WriteLine("===== 异步回调 AsyncInvokeTest =====");
            AddHandler handler = new AddHandler(加法类.Add);

            //异步操作接口(注意BeginInvoke方法的不同！)
            IAsyncResult result = handler.BeginInvoke(1,2,new AsyncCallback(回调函数),"AsycState:OK");
            
            Console.WriteLine("继续做别的事情。。。");
            Console.ReadKey();
        }

        static void 回调函数(IAsyncResult result)
        {      

            //result 是“加法类.Add()方法”的返回值
            //AsyncResult 是IAsyncResult接口的一个实现类，引用空间：System.Runtime.Remoting.Messaging
            //AsyncDelegate 属性可以强制转换为用户定义的委托的实际类。
            AddHandler handler = (AddHandler)((AsyncResult)result).AsyncDelegate;
            Console.WriteLine(handler.EndInvoke(result));
            Console.WriteLine(result.AsyncState);
        }
        
    }
}