如何跟蹤所有線程的完成情況。 C＃

Question

我需要凍結主線程直到結束遞歸。 遞歸深度=線程數。

示例代碼：

BackgroundWorker backgroundWorker1; 
    Random ran; 

    private void Form1_Load(object sender, EventArgs e) 
    { 
     method(); 
     label1.Text = "Threads is finished"; 
    } 


    private void method() // recursive method 
    { 

      Thread.Sleep(100); 

      backgroundWorker1 = new BackgroundWorker(); 

      backgroundWorker1.DoWork += 
       new DoWorkEventHandler(backgroundWorker1_DoWork); 
      backgroundWorker1.RunWorkerAsync();    //Beginning new thread 
    } 

    private void backgroundWorker1_DoWork(object sender, 
     DoWorkEventArgs e) 
    { 
      ran = new Random(); 
      Thread.Sleep(ran.Next(500, 1000)); 
      if (ran.Next(1, 5) != 1) // if = 1 then to stop recursion 
      { 
       method(); 
      } 
    } 

當線程完成時，label1.Text必須具有值"Threads is finished"。這是如何完成的？

Answer 1

控制檯應用程序PoC緩存對所有創建的工作人員的引用，並使用數字變量檢查有多少工人仍在進行中，當此值達到0時 - 應用程序終止。如有任何問題，請通知我。

class Program 
{ 
    private static IList<BackgroundWorker> workers; 
    private static Random ran; 
    private static int activeWorkersCount; 

    static void Main(string[] args) 
    {    
     workers = new List<BackgroundWorker>(); 
     DoWork(); 

     while (activeWorkersCount > 0) 
     { 
      Thread.Sleep(200); 
     } 

     Console.WriteLine("Waiting for all workers to finish..."); 
     Console.ReadLine(); 
    } 

    private static void DoWork() // recursive method 
    { 
     Thread.Sleep(100); 

     var newWorker = new BackgroundWorker(); 

     newWorker.DoWork += BackgroundWorkerDoWork; 
     newWorker.RunWorkerCompleted += (o, e) => 
       { 
        Console.WriteLine("[E] Worker finished"); 
        Interlocked.Decrement(ref activeWorkersCount); 
       }; 
     Interlocked.Increment(ref activeWorkersCount); 
     newWorker.RunWorkerAsync(); 
    } 

    private static void BackgroundWorkerDoWork(object sender, DoWorkEventArgs e) 
    { 
     Console.WriteLine("[S] Worker started"); 
     ran = new Random(); 
     Thread.Sleep(ran.Next(500, 1000)); 
     if (ran.Next(1, 5) != 1) // if = 1 then to stop recursion 
     { 
      DoWork(); 
     } 
    } 
} 

Answer 2

當您決定是時候停止遞歸時，您可以在GUI線程上發佈回調。關閉我的頭頂，它會是這樣的：

if(ran.Next(1,5)!=1) 
{ 
    method(); 
} 
else 
{ 
    Action action=()=>label1.Text = "Threads is finished"; 
    this.BeginInvoke(action); 
} 

Answer 3

1）創建，更新Label1的方法：

private void WorkFinished() 
{ 
    if(Label1.InvokeRequired) 
    { 
     Label1.Invoke(WorkFinished); 
    } 
    else 
    { 
     Label1.Text = "Threads is finished"; 
    } 
} 

2）請從backgroundWorker1_DoWork WorkFinished（）。

Answer 4

您可以使用CountDownEvent類：

例子：

using (CountDownEvent countdownEvent = new CountdownEvent(numberOfThreads)) 
{ 
    for (int threadIndex= 0; i < numberOfThreads; threadIndex++) 
     ThreadPool.QueueUserWorkItem(
      th => 
      { 
       DoWork(); 
       countdownEvent.Signal(); 
      }, threadIndex); 

    countdownEvent.Wait(); 
} 
Console.WriteLine("All threads complete"); 

Answer 5

我做到了使用揮發性整數，而且運作良好。

BackgroundWorker backgroundWorker1;  
    Random ran; 
    long runningThreads = 0; 
    public void Start()  
    {   
     method();   
     // Console.WriteLine("Threads is finished");  
    }  
    private void method() // recursive method  
    { 
     Interlocked.Increment(ref runningThreads); 
     Console.WriteLine("New thread started"); 
     Thread.Sleep(100);    
     backgroundWorker1 = new BackgroundWorker();    
     backgroundWorker1.DoWork +=     
      new DoWorkEventHandler(backgroundWorker1_DoWork);    
     backgroundWorker1.RunWorkerAsync();    //Beginning new thread  
    }  
    private void backgroundWorker1_DoWork(object sender,  DoWorkEventArgs e)  
    {    
     ran = new Random();    
     Thread.Sleep(ran.Next(500, 1000));    
     if (ran.Next(1, 5) != 1) // if = 1 then to stop recursion    
     {     
      method();    
     } 
     Finished(); 
    } 
    private void Finished() 
    { 
     Interlocked.Decrement(ref runningThreads); 
     if (Interlocked.Read(ref runningThreads) == 0) 
     { 
      Console.WriteLine("Threads is finished");  

     } 
    }