Stopwatch watch = new Stopwatch();            

//跑步计时
watch.Start();
Thread.Sleep(5000);
Console.WriteLine("甲用时：" + watch.ElapsedMilliseconds);
Thread.Sleep(500);
Console.WriteLine("乙用时：" + watch.ElapsedMilliseconds);
Thread.Sleep(500);
Console.WriteLine("丙用时：" + watch.ElapsedMilliseconds);
watch.Stop();

//任务计时
watch.Restart();
Thread.Sleep(3000);
Console.WriteLine("第一阶段用时：" + watch.ElapsedMilliseconds);
watch.Restart();
Thread.Sleep(1000);
Console.WriteLine("第二阶段用时：" + watch.ElapsedMilliseconds);
watch.Restart();
Thread.Sleep(2000);
Console.WriteLine("第三阶段用时：" + watch.ElapsedMilliseconds);
watch.Stop();