c# TimeSpan 计算时间列表差值后求和-累计时长

---------------计算两个时间差值----------------
public static GetDateDiff(DateTieme dt1,DateTime dt2)
{
   TimeSpan timeSpan1=new TimeSpan(dt1);
   TimeSpan timeSpan2=new TimeSpan(dt2);
   TimeSpan timeSpan=timeSpan1.Subtract(timeSpan2).Duration();
   return timeSpan;
}

---------------计算累计时长------------------

public TimeSpan CalTotalDateDiff(List<Datetime,Datetime> list)

{
    TimeSpan totalSpan=new TimeSpan()
    foreach(item in list)
    {
     totalSpan+=GetDateDiff(item.startTime,item.endTime);
    }
    return totalSpan.Hours.ToString()+":"+totalSpan.Minutes.ToString()+":"+totalSpan.Seconds.ToString();
}