System.Diagnostics.Stopwatch watch = new System.Diagnostics.Stopwatch();//初始化一个对象
            watch.Start();//开始计时
            //计时代码
            StringBuilder sb = new StringBuilder(2000);
            for (int i = 0; i < 10000000; i++)
            {
                sb.Append(i.ToString());
            }
            watch.Stop();//停止计时
            System.Diagnostics.Debug.WriteLine("耗时:" + watch.Elapsed);//输出时间 毫秒