C# 事件（2）

下边Demo如果是在vs2012 下运行需要进入调试模式，并且用合理的速度调试一遍才能正常运行出结果。

namespace ConsoleApplication2
{
    public delegate void MessageHanlder(Connection source, MessageArrivedEventArgs e);

    public class Connection
    {
        public event MessageHanlder MessageArried;
        private Timer pollTimer;

        public string name { get; set; }

        public Connection()
        {
            pollTimer = new Timer(700);
            pollTimer.Elapsed += new ElapsedEventHandler(CheckForMsg);
        }

        public void Connect()
        {
            pollTimer.Start();
        }

        public void DisConnect()
        {
            pollTimer.Stop();
        }

        private static Random random = new Random();

        void CheckForMsg(object sources, ElapsedEventArgs e)
        {
            Console.WriteLine("Checking for new messages");
            if ((random.Next(9) == 0) && (MessageArried != null))//使用了委托语法，但语法略有不同，其含义为“事件是否有订阅者？”如果没有订阅者，MessageArrived就是null，也就不会引发事件。
            {
                MessageArried(this, new MessageArrivedEventArgs("Hello Mum!"));
            }
        }
    }

    class Display
    {
        public void DisplayMsg(Connection source, MessageArrivedEventArgs e)
        {
            Console.WriteLine("message arrived from:{0}", source.name);
            Console.WriteLine("message Text:{0}", e.Message);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Connection conn1 = new Connection();
            conn1.name = "First conneciton";
            Connection conn2 = new Connection();
            conn2.name = "second connection";

            Display display = new Display();
            conn1.MessageArried += new MessageHanlder(display.DisplayMsg);//注册事件
            conn2.MessageArried += delegate(Connection source, MessageArrivedEventArgs e)//匿名方式注册事件
            {
                Console.WriteLine("dddddddddd message arrived from:{0}", source.name);
                Console.WriteLine("dddddddddd message Text:{0}", e.Message);
            };

            conn2.Connect();
            conn1.Connect();
            Console.ReadKey();
        }
    }

    public class MessageArrivedEventArgs : EventArgs
    {
        private string message;
        public string Message
        {
            get { return message; }
        }

        public MessageArrivedEventArgs()
        {
            message = "No message sent";
        }

        public MessageArrivedEventArgs(string newmsge)
        {
            message = newmsge;
        }
    }
}