高级编程里的一个例子，我见很好啊。

程序代码：

using System;
using System.Collections;
using System.Windows.Forms;

namespace Event
{
    enum RequestType
    {
        AdRequest,
        PersonMessageRequest    
    };
    //事件处理类UserRequestEventArgs，没必要继承EventArgs，
    //EventArgs又没有提供虚函数（也没必要提供）
    class UserRequestEventArgs
    {
        private RequestType request;
        public UserRequestEventArgs(RequestType request)
        {
            this.request=request;
        }
        public RequestType Request
        {
            get
            {
                return request;
            }
        }
    }
    class UserInputMonitor
    {
        //事件委托
        public delegate void UserRequest(object sender,UserRequestEventArgs e);
        //Event关键字说明这个委托是个事件
        public event UserRequest OnUserRequest;
        public UserInputMonitor()
        {
            //绑定事件处理方法
            OnUserRequest += new Event.UserInputMonitor.UserRequest(monitor_OnUserRequest);
        }
        public void Run()
        {
            Console.WriteLine(\"Input:\");
            while(true)
            {
                //输入A则显示AdRequest，输入P则显示PersonMessageRequest
                string response = Console.ReadLine();
                char responseChar = (response==\"\")?' ':char.ToUpper(response[0]);
                switch(responseChar)
                {
                    case 'A':
                        this.OnUserRequest(this,new UserRequestEventArgs(RequestType.AdRequest));
                        break;
                    case 'P':
                        this.OnUserRequest(this,new UserRequestEventArgs(RequestType.PersonMessageRequest));
                        break;
                    case 'X':
                        return;
                }
            }
        }
        //事件处理方法
        protected void monitor_OnUserRequest(object sender,UserRequestEventArgs e)
        {
            //根据枚举值决定显示的信息
            switch(e.Request)
            {
                case RequestType.AdRequest:
                    MessageBox.Show(\"It's AdRequest!\");
                    break;
                case RequestType.PersonMessageRequest:
                    MessageBox.Show(\"It's PersonMessageRequest!\");
                    break;
            }
        }
    }
    class AppMain
    {
        public AppMain()
        {}
        static void Main()
        {
            UserInputMonitor user = new UserInputMonitor();
            user.Run();
            Console.ReadLine();
        }
    }
}