static System.Threading.Timer timer; 
        static void Main(string[] args)
        {
            Console.WriteLine("Press Enter key to stop timer");
            DateTime start = DateTime.Now;
            //啟動定時器，每2秒執行一次
            timer = new Timer(p => TimerOperation(start),null,TimeSpan.FromSeconds(1
 
),TimeSpan.FromSeconds(2));
            //休眠10秒，10/2=5，即定時器執行5次
            Thread.Sleep(TimeSpan.FromSeconds(10));
            //在修改為調用change方法1秒後啟動TimerOperation，然後每5秒執行一次
            timer.Change(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(5));
            Console.ReadLine();
            timer.Dispose();
        }

        
 
static void TimerOperation(DateTime start)
        {
            TimeSpan elapsed = DateTime.Now - start;
            Console.WriteLine("{0} seconds from {1}. timer thead pool thread id : {2}",elapsed.Seconds,start,Thread.CurrentThread.ManagedThreadId);

        }

定時器&改變定時器的執行頻率