C# 程序运行耗时计算

using System;
using System.Diagnostics;
                    Stopwatch stopWatch = new Stopwatch();
                    stopWatch.Start();
                    //...........中间代码...........
                    stopWatch.Stop();
                    TimeSpan tml = stopWatch.Elapsed;
                    string elapsedTime = string.Format("{0:00} 时 {1:00} 分 {2:00} 秒 {3:00}", tml.Hours, tml.Minutes, tml.Seconds, tml.Milliseconds / 10);
                    MessageBox.Show("所有客户提取完成！\n共耗时：" + elapsedTime, "完成提醒：");