namespace 使用Semaphore { class Program { //第1個參數指定當前運行多少條線程進入，第2個參數表示 允許多少個線程同時進入 static Semaphore sem = new Semaphore(2, 2); static void Main(string[] args) { for (int i = 1; i <=4; i++) { new Thread (ThreadEntry).Start (i); } } static void ThreadEntry(object id) { Console.WriteLine("thread {0} wants to get in",id); sem.WaitOne(); //在調用waitone方法時，如果有空位，則占位；如果沒有，則等待； Console.WriteLine("thread {0} gets in",id ); Thread.Sleep(100); Console.WriteLine("thread {0} is leaving",id ); sem.Release(); //釋放1個空位； } } }