Question

c# 怎么等待线程池中所有线程都运行结束在运行主线程

主线程执行
。。。
线程1加入线程池
线程2加入线程池
线程3加入线程池
线程4加入线程池...

主线程等待线程池中加入的线程运行完毕。。。

主线程执行
。。。。

怎么实现上面的步骤？如果线程池只加入一个，那么在线程运行结束调用manulresetevent类的set（）方法即可，但是加入一个以上该怎么办呢？

Answer 1

可以参见 WaitHandle.WaitAll 方法。
WaitHandle的命名空间是System.Thread。

可以为每一个线程创建一个

WaitHandle，比如：

WaitHandle[] waitHandles = new WaitHandle[]
{
new AutoResetEvent(false),
new AutoResetEvent(false),
...
};

然后在每条线程结束时，set与之相对应的那个 WaitHandle，

在主线程中，使用

WaitHandle.WaitAll方法来等待所有的WaitHandle，

比如：
WaitHandle.WaitAll(waitHandles);

以下是MSDN中的示例代码：

using System;
using System.Threading;

public sealed class App
{
// Define an array with two AutoResetEvent WaitHandles.
static WaitHandle[] waitHandles = new WaitHandle[]
{
new AutoResetEvent(false),
new AutoResetEvent(false)
};

// Define a random number generator for testing.
static Random r = new Random();

static void Main()
{
// Queue up two tasks on two different threads;
// wait until all tasks are completed.
DateTime dt = DateTime.Now;
Console.WriteLine("Main thread is waiting for BOTH tasks to complete.");
ThreadPool.QueueUserWorkItem(new WaitCallback(DoTask), waitHandles[0]);
ThreadPool.QueueUserWorkItem(new WaitCallback(DoTask), waitHandles[1]);
WaitHandle.WaitAll(waitHandles);
// The time shown below should match the longest task.
Console.WriteLine("Both tasks are completed (time waited={0})",
(DateTime.Now - dt).TotalMilliseconds);

// Queue up two tasks on two different threads;
// wait until any tasks are completed.
dt = DateTime.Now;
Console.WriteLine();
Console.WriteLine("The main thread is waiting for either task to complete.");
ThreadPool.QueueUserWorkItem(new WaitCallback(DoTask), waitHandles[0]);
ThreadPool.QueueUserWorkItem(new WaitCallback(DoTask), waitHandles[1]);
int index = WaitHandle.WaitAny(waitHandles);
// The time shown below should match the shortest task.
Console.WriteLine("Task {0} finished first (time waited={1}).",
index + 1, (DateTime.Now - dt).TotalMilliseconds);
}

static void DoTask(Object state)
{
AutoResetEvent are = (AutoResetEvent) state;
int time = 1000 * r.Next(2, 10);
Console.WriteLine("Performing a task for {0} milliseconds.", time);
Thread.Sleep(time);
are.Set();
}
}

// This code produces output similar to the following:
//
// Main thread is waiting for BOTH tasks to complete.
// Performing a task for 7000 milliseconds.
// Performing a task for 4000 milliseconds.
// Both tasks are completed (time waited=7064.8052)
//
// The main thread is waiting for either task to complete.
// Performing a task for 2000 milliseconds.
// Performing a task for 2000 milliseconds.
// Task 1 finished first (time waited=2000.6528).

Answer 2

您能自己在msdn上先看看thread的相关方法和资料吗。。。。这都是太基础的问题了。。。。

http://www.microsoft.com/china/msdn/

http://msdn.microsoft.com/zh-cn/library/default.aspx