多線程13-CountdownEvent

     class Program
    {
         static CountdownEvent _countdownEvent =  new CountdownEvent( 2);
         static  void PerformOperation( string message, int second)
        {
            Thread.Sleep(TimeSpan.FromSeconds(second));
            Console.WriteLine(message);
            _countdownEvent.Signal();
        }
         static  void Main()
        {
            Console.WriteLine( " Starting two operations ");
             var t1 =  new Thread(() => PerformOperation( " Opearation1 is completed ",  4));
             var t2 =  new Thread(() => PerformOperation( " Opeartion2 is compled ",  2));
            t1.Start();
            t2.Start();
            _countdownEvent.Wait();
            Console.WriteLine( " Both operations have been compled ");             _countdownEvent.Dispose();         }     }