C# 事件（1）

下边Demo如果是在vs2012 下运行需要进入调试模式一遍才能正常运行出结果

namespace ConsoleApplication2
{
    public delegate void messageHandler(string msg);

    public class Connection
    {
        public event messageHandler MessageArried;

        private Timer pollTimer;

        public Connection()
        {
            pollTimer = new Timer(100);
            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("Hello Mum!");
            }
        }
    }

    class Display
    {
        public void DisplayMsg(string message)
        {
            Console.WriteLine("Msg arrived:{0}", message);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Connection conn = new Connection();
            Display display = new Display();
            conn.MessageArried += new messageHandler(display.DisplayMsg);
            conn.Connect();

            Console.ReadKey();

        }

    }
}