C# ManualResetEvent用法详解

2020-01-24 00:01:17

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ManualResetEvent表示线程同步事件，可以对所有进行等待的线程进行统一管理（收到信号时必须手动重置该事件）

其构造函数为：

public ManualResetEvent (bool initialState);

参数 initialState 表示是否初始化，如果为 true，则将初始状态设置为终止（不阻塞）；如果为 false，则将初始状态设置为非终止（阻塞）。

注意：如果其参数设置为true，则ManualResetEvent等待的线程不会阻塞。如果初始状态为false, 则在Set调用方法之前, 将阻止线程。

它只有两个方法

//将事件状态设置为终止状态，从而允许继续执行一个或多个等待线程。public bool Set ();//将事件状态设置为非终止，从而导致线程受阻。public bool Reset ();//返回值：操作成功返回true，否则false

讲了这么多，看个例子理解一下

using System;using System.Threading;public class Example{  // mre is used to block and release threads manually. It is  // created in the unsignaled state.  private static ManualResetEvent mre = new ManualResetEvent(false);  static void Main()  {    Console.WriteLine("/nStart 3 named threads that block on a ManualResetEvent:/n");    for (int i = 0; i <= 2; i++)    {      Thread t = new Thread(ThreadProc);      t.Name = "Thread_" + i;      t.Start(); //开始线程    }    Thread.Sleep(500);    Console.WriteLine("/nWhen all three threads have started, press Enter to call Set()" +             "/nto release all the threads./n");    Console.ReadLine();    mre.Set();    Thread.Sleep(500);    Console.WriteLine("/nWhen a ManualResetEvent is signaled, threads that call WaitOne()" +             "/ndo not block. Press Enter to show this./n");    Console.ReadLine();    for (int i = 3; i <= 4; i++)    {      Thread t = new Thread(ThreadProc);      t.Name = "Thread_" + i;      t.Start();    }    Thread.Sleep(500);    Console.WriteLine("/nPress Enter to call Reset(), so that threads once again block" +             "/nwhen they call WaitOne()./n");    Console.ReadLine();    mre.Reset();    // Start a thread that waits on the ManualResetEvent.    Thread t5 = new Thread(ThreadProc);    t5.Name = "Thread_5";    t5.Start();    Thread.Sleep(500);    Console.WriteLine("/nPress Enter to call Set() and conclude the demo.");    Console.ReadLine();    mre.Set();    // If you run this example in Visual Studio, uncomment the following line:    //Console.ReadLine();  }  private static void ThreadProc()  {    string name = Thread.CurrentThread.Name;    Console.WriteLine(name + " starts and calls mre.WaitOne()");    mre.WaitOne(); //阻塞线程，直到调用Set方法才能继续执行    Console.WriteLine(name + " ends.");  }}

结果如下