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C# 多线程等待子线程全部完成 ThreadPool

private void button1_Click(object sender, EventArgs e)
       { 
            
           //假设有10个请求线程
           int num = 10;
           using (MultiThreadResetEvent multiThreadResetEvent = new MultiThreadResetEvent(num))
           {
               for (int i = 0; i < num; i++)
               {
                   //ManualResetEvent manualResetEvent = new ManualResetEvent(false);
                   Param pra = new Param();
                   pra.multiThreadResetEvent = multiThreadResetEvent;
                   pra.value = i;
                   //manualResetEvents.Add(manualResetEvent);
                   ThreadPool.QueueUserWorkItem(Call, pra);
 
               }
               //WaitHandle.WaitAll(manualResetEvents.ToArray());
 
               multiThreadResetEvent.WaitAll();
           }
       
           Console.WriteLine("main thread is success");
       }

private void Call(object state)
      {
          Thread.Sleep(1000);
          Param param = state as Param;
 
 
          Console.WriteLine($"Thread execute {param.value} --- {DateTime.Now}  ");
          param.multiThreadResetEvent.SetOne(); 
      }

public  class Param
{
    public Param()
    {
    }
 
    public MultiThreadResetEvent multiThreadResetEvent { get;  set; }
    public int value { get;  set; }
}

/// <summary>
  /// 多线程信号等待
  /// </summary>
  public class MultiThreadResetEvent : IDisposable
  {
      private readonly ManualResetEvent done;
      private readonly int total;
      private long current;
 
      /// <summary>
      /// 监视total个线程执行（线程数固定，可以超过64个）
      /// </summary>
      /// <param name="total">需要等待执行的线程总数</param>
      public MultiThreadResetEvent(int total)
      {
          this.total = total;
          current = total;
          done = new ManualResetEvent(false);
      }
 
      /// <summary>
      /// 线程数不固定，监视任意线程数时
      /// </summary>
      public MultiThreadResetEvent()
      {
          done = new ManualResetEvent(false);
      }
 
      /// <summary>
      /// 加入一个要等待的线程信号
      /// </summary>
      public void addWaitOne()
      {
          Interlocked.Increment(ref current);
      }
      /// <summary>
      /// 唤醒一个等待的线程
      /// </summary>
      public void SetOne()
      {
          // Interlocked 原子操作类 ,此处将计数器减1
          if (Interlocked.Decrement(ref current) == 0)
          {
              //当所以等待线程执行完毕时，唤醒等待的线程
              done.Set();
          }
      }
      /// <summary>
      /// 等待所以线程执行完毕
      /// </summary>
      public void WaitAll()
      {
          done.WaitOne();
      }
      /// <summary>
      /// 释放对象占用的空间
      /// </summary>
      public void Dispose()
      {
          ((IDisposable)done).Dispose();
      }
  }