span.kw { color: #007020; font-weight: bold; }
code > span.dt { color: #902000; }
code > span.dv { color: #40a070; }
code > span.bn { color: #40a070; }
code > span.fl { color: #40a070; }
code > span.ch { color: #4070a0; }
code > span.st { color: #4070a0; }
code > span.co { color: #60a0b0; font-style: italic; }
code > span.ot { color: #007020; }
code > span.al { color: #ff0000; font-weight: bold; }
code > span.fu { color: #06287e; }
code > span.er { color: #ff0000; font-weight: bold; }
-->

一个事件的发生需要有触发条件，如定时发生，鼠标点击等，以及即将发生的事件本身，因此，events相关的最简单的示例如下：

// 时间触发器

class TimerTrigger

{

    private Timer myTimer;

    public TimerTrigger()

    {

        myTimer = new Timer(100);

    }

    public TimerTrigger(int timeInterval)

    {

        myTimer = new Timer(timeInterval);

    }

    // 向时间触发器添加具事件的handler

    public void AddEventHander(ElapsedEventHandler source)

    {

        myTimer.Elapsed += source;

    }

    public void Start()

    {

        myTimer.Start();

    }

    public void Stop()

    {

        myTimer.Stop();

    }

}

class Program

{

    static int counter = 0;

    static string displayString =

        "This string will appear one letter at a time. ";

    // 即将被添加到时间触发器的事件

    static void WriteChar(object source, ElapsedEventArgs e)

    {

        Console.Write(displayString[counter++ % displayString.Length]);

    }

    public static void Main()

    {

        TimerTrigger timerTrigger = new TimerTrigger(100);

        timerTrigger.AddEventHander(new ElapsedEventHandler(WriteChar));

        timerTrigger.Start();

        Console.ReadLine();

    }

}

在上面的例子的main函数中，直接使用了c#自带的ElapsedEventHandler delegated类型，那么如何自定义事件处理函数呢？具体如下：

// 自定义时间处理代表

public delegate void MessageHandler(string message);

class TimerTrigger

{

    private Timer myTimer;

    private event MessageHandler MessageArrived;

    public TimerTrigger(int timeInterval)

    {

        myTimer = new Timer(timeInterval);

        myTimer.Elapsed += new ElapsedEventHandler(CheckForMessage);

    }

    public void AddEventHandler(MessageHandler source)

    {

        MessageArrived += source;

    }

    public void Start()

    {

        myTimer.Start();

    }

    public void Stop()

    {

        myTimer.Stop();

    }

    private void CheckForMessage(object source, ElapsedEventArgs e)

    {

        Console.WriteLine("Checking for new messages.");

        if (MessageArrived != null)

        {

            MessageArrived("hello world");

        }

    }

}

class Program

{

    static int counter = 0;

    static void WriteFirstMessage(string message)

    {

        Console.WriteLine("The First {0} number: {1}", message, counter++);

    }

    static void WriteSecondMessage(string message)

    {

        Console.WriteLine("The Second {0} number: {1}", message, counter++);

    }

    public static void Main()

    {

        TimerTrigger timerTrigger = new TimerTrigger(100);

        timerTrigger.AddEventHandler(new MessageHandler(WriteFirstMessage));

        timerTrigger.AddEventHandler(new MessageHandler(WriteSecondMessage));

        timerTrigger.Start();

        Console.ReadLine();

    }

}

在上述的例子中，将消息传递给处理事件所用的函数为WriteFirstMessage(string message)，其传递的参数为string类型的。再考虑道<Timer>.ElapsedEventHandler所代表的函数的传递参数为：(object source, ElapsedEventArgs e)两个参数，那么我们能否实现类似的形式呢？这是可以的，如下：

public class MessageArrivedEventArgs : EventArgs

{

    private string message;

    public string Message

    {

        get

        {

            return message;

        }

    }

    public MessageArrivedEventArgs()

    {

        message = "No message sent.";

    }

    public MessageArrivedEventArgs(string newMessage)

    {

        message = newMessage;

    }

}

public delegate void MessageHandler(TimerTrigger source,

    MessageArrivedEventArgs e);

public class TimerTrigger

{

    private Timer myTimer;

    private event MessageHandler MessageArrived;

    public TimerTrigger(int timeInterval)

    {

        myTimer = new Timer(timeInterval);

        myTimer.Elapsed += new ElapsedEventHandler(CheckForMessage);

    }

    public void AddEventHandler(MessageHandler source)

    {

        MessageArrived += source;

    }

    public void Start()

    {

        myTimer.Start();

    }

    public void Stop()

    {

        myTimer.Stop();

    }

    private void CheckForMessage(object source, ElapsedEventArgs e)

    {

        Console.WriteLine("Checking for new messages.");

        if (MessageArrived != null)

        {

            MessageArrived(this, new MessageArrivedEventArgs("hello world"));

        }

    }

}

class Program

{

    static int counter = 0;

    static void WriteFirstMessage(TimerTrigger source, MessageArrivedEventArgs e)

    {

        Console.WriteLine("The First {0} number: {1}", e.Message, counter++);

    }

    static void WriteSecondMessage(TimerTrigger source, MessageArrivedEventArgs e)

    {

        Console.WriteLine("The Second {0} number: {1}", e.Message, counter++);

    }

    public static void Main()

    {

        TimerTrigger timerTrigger = new TimerTrigger(100);

        timerTrigger.AddEventHandler(new MessageHandler(WriteFirstMessage));

        timerTrigger.AddEventHandler(new MessageHandler(WriteSecondMessage));

        timerTrigger.Start();

        Console.ReadLine();

    }

}