stopwatch vs timeSpan

talk waste time, show code!

 DateTime dtstart = DateTime.Now; //分步骤时长计数
 TimeSpan spanTime;
 double dtime;

   dtstart = DateTime.Now; 

{ do something.......}
 spanTime = (TimeSpan)(DateTime.Now - dtstart);
 dtime = spanTime.TotalMilliseconds;
 Utils._log.Info("时间开销:" + dtime);

stopwatch:

  Stopwatch stopwatch = new Stopwatch();

  stopwatch.Start();
{
    do something.......
}

  stopwatch.Stop();
  Console.WriteLine($"调用耗时3: {stopwatch.ElapsedMilliseconds} 毫秒");