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。
            }
        }
    }
}