c#的程序执行时间计算类

    public class TimerHelper
    {
        Stopwatch sw;
        TimeUnit _timeUnit;

        public TimerHelper()
        {
            _timeUnit = TimeUnit.Millisecond;

            sw = new Stopwatch();
            sw.Start();
        }

        public TimerHelper(TimeUnit timeUnit)
        {
            _timeUnit = timeUnit;

            sw = new Stopwatch();
            sw.Start();
        }

        public string Finish() 
        {
            sw.Stop();

            if (_timeUnit == TimeUnit.Millisecond)
                return sw.ElapsedMilliseconds.ToString("0.##") + " ms";
            else if (_timeUnit == TimeUnit.Second)
                return sw.Elapsed.TotalSeconds.ToString("0.##") + " s";
            else if (_timeUnit == TimeUnit.Minute)
                return sw.Elapsed.TotalMinutes.ToString("0.##") + " mins";
            else if (_timeUnit == TimeUnit.Hour)
                return sw.Elapsed.TotalHours.ToString("0.##") + " hrs";
            else if (_timeUnit == TimeUnit.Day)
                return sw.Elapsed.TotalDays.ToString("0.##") + " days";
            else
                return "NOT SUPPORTED";
            
        }
    }
   //返回时间格式
    public enum TimeUnit
    {
        Millisecond,
        Second,
        Minute,
        Hour,
        Day
    }

TimerHelper timing = new TimerHelper(TimeUnit.Second);

//做什么

 var time= timing.Finish();//返回执行时间