c#等待所有子线程执行完毕方法

当我们在使用线程中，你会发现主线结束后子线程的结果才显示出来。现在我要等待所以子线程结束，然后在显示结果，怎么做呢？

方法如下：

1、使用 ManualResetEvent，代码如下：

using System.Threading;

namespace ThreadStudy
{
/// <summary>
/// 等待所有子线程结束
/// </summary>
class StopAllWaitBySubThread
{
List<ManualResetEvent> manualEvents = new List<ManualResetEvent>();
public void Main()
{
for (int i = 0; i < 5; i++)
{
ManualResetEvent mre = new ManualResetEvent(false);
manualEvents.Add(mre);
ThreadPool.QueueUserWorkItem(ThreadMethod, mre);
}
WaitHandle.WaitAll(manualEvents.ToArray());
Console.WriteLine("Thread Finished!");
}

private void ThreadMethod(object obj)
{
//等待2秒，用于模拟系统在处理事情
Thread.Sleep(2000);

ManualResetEvent mre = (ManualResetEvent)obj;
mre.Set();
Console.WriteLine("Thread execute");
}
}
}

此种方法线程中只传递了信号，那要传递参数怎么办？可以采用类，将信号放在类中来解决，代码如下。

using System.Threading;

namespace ThreadStudy
{
/// <summary>
/// 等待所有子线程结束
/// </summary>
class StopAllWaitBySubThread
{
List<ManualResetEvent> manualEvents = new List<ManualResetEvent>();
public void Main()
{
for (int i = 0; i < 5; i++)
{
ManualResetEvent mre = new ManualResetEvent(false);
manualEvents.Add(mre);
Param pra = new Param();
pra.mrEvent = mre;
pra.praData = i;
ThreadPool.QueueUserWorkItem(ThreadMethod, pra);
}
WaitHandle.WaitAll(manualEvents.ToArray());
Console.WriteLine("Thread Finished!");
}

private void ThreadMethod(object obj)
{
Thread.Sleep(2000);
Param pra = (Param)obj;
pra.mrEvent.Set();
Console.WriteLine("Thread execute at {0}", pra.praData);
}
}

public class Param
{
public ManualResetEvent mrEvent;
public int praData;
}
}

2、判断线程数

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.Threading;

namespace ThreadStudy
{
/// <summary>
/// 判断当所有子线程执行完毕
/// </summary>
class ThreadPoolStop
{
public void Main()
{
for (int i = 0; i < 5; i++)
{
ThreadPool.QueueUserWorkItem(new WaitCallback(ThreadMethod), i);
}
int maxWorkerThreads, workerThreads;
int portThreads;
while (true)
{
/*
GetAvailableThreads()：检索由 GetMaxThreads 返回的线程池线程的最大数目和当前活动数目之间的差值。
而GetMaxThreads 检索可以同时处于活动状态的线程池请求的数目。
通过最大数目减可用数目就可以得到当前活动线程的数目，如果为零，那就说明没有活动线程，说明所有线程运行完毕。
*/
ThreadPool.GetMaxThreads(out maxWorkerThreads, out portThreads);
ThreadPool.GetAvailableThreads(out workerThreads, out portThreads);
if (maxWorkerThreads - workerThreads == 0)
{
Console.WriteLine("Thread Finished!");
break;
}
}
}

private void ThreadMethod(object i)
{

//模拟程序运行

Thread.Sleep((new Random().Next(1, 4)) * 1000);
Console.WriteLine("Thread execute at {0}", i.ToString());
}
}
}

3、使用Monitor

using System.Threading;

namespace ThreadStudy
{
class StopAllSubThread
{
int _ThreadCount = 5;
int finishcount = 0;
object locker = new object();
public void Main()
{
for (int i = 0; i < _ThreadCount; i++)
{
Thread trd = new Thread(new ParameterizedThreadStart(ThreadMethod));
trd.Start(i);
}
lock (locker)
{
while (finishcount != _ThreadCount)
{
Monitor.Wait(locker);//等待
}
}
Console.WriteLine("Thread Finished!");
}

private void ThreadMethod(object obj)
{
//模拟执行程序
Thread.Sleep(3000);
Console.WriteLine("Thread execute at {0}", obj.ToString());
lock (locker)
{
finishcount++;
Monitor.Pulse(locker); //完成，通知等待队列,告知已完，执行下一个。
}
}
}
}