线程之间灵活传递信号（ManualResetEventSlim ）

当主程序启动时，首先创建ManualResetEventSlim 类的一个实例。然后启动三个线程，等待事件信号通知它们继续执行。

 /// <summary>
         /// 创建 ManualResetEventSlim 实例
         /// </summary>
         private static ManualResetEventSlim _mainEvent = new ManualResetEventSlim(false);

         /// <summary>
         /// 接收信号继续执行
         /// </summary>
         /// <param name="threadName">线程名</param>
         /// <param name="secods">时间（秒）</param>
         public void TravelThroughGates(string threadName, int secods)
         {
             // threadName  falls to sleep
             System.Threading.Thread.Sleep(TimeSpan.FromSeconds(secods));

             // threadName waits for the gates to open
             _mainEvent.Wait();      // 阻止当前线程，直到接收到信号

             // threadName enters the gates
             Console.WriteLine($"{threadName} 继续执行");

         }

线程只有在ManualResetEventSlim 对象发出信号才能继续执行，不然只有继续等待，直到接接收到信号。

 /// <summary>
         /// 输出
         /// </summary>
         public void Print()
         {
             var t1 = new System.Threading.Thread(() => TravelThroughGates("Thread 1", ));
             var t2 = new System.Threading.Thread(() => TravelThroughGates("Thread 2", ));
             var t3 = new System.Threading.Thread(() => TravelThroughGates("Thread 3", ));

             t1.Start();
             t2.Start();
             t3.Start();
             System.Threading.Thread.Sleep(TimeSpan.FromSeconds());

             // The gates are now open
             _mainEvent.Set();   // 发射信号

             System.Threading.Thread.Sleep(TimeSpan.FromSeconds());
             _mainEvent.Reset();     // 关闭信号

             // The gates have been closed
             System.Threading.Thread.Sleep(TimeSpan.FromSeconds());

             // The gates are now open for the second time
             _mainEvent.Set();   // 发射信号

             System.Threading.Thread.Sleep(TimeSpan.FromSeconds());

             //The gates have been closed
             _mainEvent.Reset();     // 关闭信号
         }