两个时间段差值，返回小时，分钟

           private string DateDiff(string qsTime, string zzTime)
        {
            DateTime ksTime = DateTime.Parse(qsTime);
            DateTime jsTime = DateTime.Parse(zzTime);

            string dateDiff = null;
            TimeSpan ts1 = new TimeSpan(ksTime.Ticks);
            TimeSpan ts2 = new TimeSpan(jsTime.Ticks);
            TimeSpan ts = ts1.Subtract(ts2).Duration();
            dateDiff = ts.Hours.ToString() + " : " + ts.Minutes.ToString();
            return dateDiff;
        }