ASP.NET时间差（TimeSpan用法）

       public static string TimeType(DateTime tm)        {            string timeNumber = string.Empty;                       DateTime timeNow = DateTime.Now;            TimeSpan ts = timeNow - tm;            int minNum = ts.Minutes;            int hoursNum = ts.Hours;            int dayNum = ts.Days;            if (dayNum < 1 && hoursNum < 1)            {                timeNumber = minNum.ToString() + "分钟前";            }            else if (dayNum < 1 && hoursNum > 1)            {                timeNumber = hoursNum.ToString() + "小时前";            }            else if (dayNum >= 1 && dayNum <= 3)            {                timeNumber = dayNum.ToString() + "天前";            }            else if (dayNum > 3)            {                timeNumber = tm.ToString();            }            return timeNumber;        }