等待未知數量的任務，然後阻止任何新的任務

Question

什麼是.NET中最好的同步原語/模式，等待未知數量的線程/任務完成後立即阻止任何新的執行？

基本上類似於任務集合Add和WaitForAllThenDispose。 WaitForAllThenDispose允許在等待期間添加新任務並正確等待所有這些任務。

但是，只要所有活動任務都完成並且沒有對Add的併發調用，它就會處理並阻止添加任何新任務。

Answer 1

模式我在此刻結束：

public class ActionScheduler { 
    private readonly CountdownEvent _allCompleted = new CountdownEvent(1); 
    private volatile bool _disposed; 

    public void Schedule(Action action) { 
     if (_disposed) 
      throw new ObjectDisposedException("ActionScheduler"); 

     // this feels ugly: 
     try { 
      _allCompleted.AddCount(); 
     } 
     catch (InvalidOperationException) { 
      // should only happen after the dispose/wait has completed 
      throw new ObjectDisposedException("ActionScheduler"); 
     } 

     ScheduleInternal(() => { 
      try { 
       action(); 
      } 
      finally { 
       _allCompleted.Signal(); 
      } 
     }); 
    } 

    private void ScheduleInternal(Action action) { 
     // some async scheduling irrelevant to the example 
    } 

    public void Dispose() { 
     if (_disposed) 
      return; 

     _allCompleted.Signal(); // removing initial +1 
     _allCompleted.Wait(); 
     _disposed = true; 
    } 
}