关于AutoResetEvent、TimeSpan

有点明白了，赶紧记下来。

using System;
using System.Threading;

class TimerExample
{
    static void Main()
    {
       // AutoResetEvent类的作用就在于可以让等待的线程继续
	AutoResetEvent autoEvent = new AutoResetEvent(false);
        StatusChecker statusChecker = new StatusChecker(10);

        // Create the delegate that invokes methods for the timer.
        TimerCallback timerDelegate =
            new TimerCallback(statusChecker.CheckStatus);

        TimeSpan delayTime = new TimeSpan(0, 0, 2);//两秒的时间
        TimeSpan intervalTime = new TimeSpan(0, 0, 0, 0, 250);//1/4秒的时间

        // Create a timer that signals the delegate to invoke 
        // CheckStatus after one second, and every 1/4 second 
        // thereafter.
        Console.WriteLine("{0} Creating timer.\n",
            DateTime.Now.ToString("h:mm:ss.fff"));
        Timer stateTimer = new Timer(
            timerDelegate, autoEvent, delayTime, intervalTime);//这个timer在开始调用timerDelegate之前停留delayTime长的时间，并每隔intervalTime长的时间重新调用一次。autoEvent这个参数很关键，当timerDelegate被调用时，就是调用的参数，可以被执行的函数所用
        Console.WriteLine("********开始了*********");
        // When autoEvent signals, change the period to every 
        // 1/2 second.
        autoEvent.WaitOne(3000, false);//这里进程会停留一段时间，比如这里设定的3秒。在这3秒内，stateTimer 将发挥其作用，不断的调用timerDelegate。但是，这里只有3秒的时间让其发挥，超过三秒后，进程会继续往下执行，stateTimer 会被重新设定。当然，如果这里停留的时间够长，长到足够stateTimer 发挥完其作用，直到timerDelegate会强制进程继续从而改变stateTimer 
        stateTimer.Change(new TimeSpan(0),
            intervalTime + intervalTime);
        Console.WriteLine("\nChanging period.\n");

        // When autoEvent signals the second time, dispose of 
        // the timer.
        autoEvent.WaitOne(50000, false);
        stateTimer.Dispose();
        Console.WriteLine("\nDestroying timer.");
        Console.ReadLine();
    }
}

class StatusChecker
{
    int invokeCount, maxCount;

    public StatusChecker(int count)
    {
        invokeCount = 0;
        maxCount = count;
    }

    // This method is called by the timer delegate.
    public void CheckStatus(Object stateInfo)
    {
        AutoResetEvent autoEvent = (AutoResetEvent)stateInfo;
        Console.WriteLine("{0} Checking status {1,2}.",
            DateTime.Now.ToString("h:mm:ss.fff"),
            (++invokeCount).ToString());

        if (invokeCount == maxCount)
        {
            // Reset the counter and signal Main.
            invokeCount = 0;
            autoEvent.Set();
        }
    }
}