C#使用Timer类和Join方法管理线程

Timer类允许将"fire-and-forget"线程添加到用户程序。在实例化Timer对象时，需要指定以下4个参数

• callback　　提供Timer将调用方法的TimerCallback委托
• state　　应该传递给TimerCallback方法的对象。这个参数可为null
• dueTime　　Timer首次激发之前延迟的毫秒数
• Period　　Timer调用之间的毫秒数。

以下为Timer的一个示例：

/*
  Example14_5.cs illustrates the use of the Timer class
 */

 using System;
 using System.Threading;

class Example14_5 
{

    // the CheckTime method is called by the Timer
    public static void CheckTime(Object state) 
    {
        Console.WriteLine(DateTime.Now);
    }

    public static void Main() 
    {

        // create the delegate that the Timer will call
        TimerCallback tc = new TimerCallback(CheckTime);

        // create a Timer that runs twice a second, starting in one second
        Timer t = new Timer(tc, null, 1000, 500);

        // Wait for user input
        Console.WriteLine("Press Enter to exit");
        int i = Console.Read();

        // clean up the resources
        t.Dispose();
        t = null;

    }

}

Thread.Join方法允许“持有” 某个线程，直至另一个线程完成其工作。如：

/*
  Example14_6.cs shows the Thread.Join method in action
*/

using System;
using System.Threading;

class Example14_6 
{

    // the Countdown method counts down from 1000 to 1
    public static void Countdown() 
    {
        for (int counter = 1000; counter > 0; counter--) 
        {
            Console.Write(counter.ToString() + " ");
        }
    }

    public static void Main() 
    {

        // create a second thread
        Thread t2 = new Thread(new ThreadStart(Countdown));

        // launch the second thread
        t2.Start();

        // block the first thread until the second is done
        t2.Join();

        // and  call the Countdown method from the first thread
        Countdown();

    }

}