C#中如何获得两个日期之间的天数差 （ c# 计算两个日期之间相差的天数 ）

DateTime dtLast = new DateTime(Convert.ToInt32(LastMenses.Year), Convert.ToInt32(LastMenses.Month), Convert.ToInt32(LastMenses.Day));

            DateTime dtThis = new DateTime(Convert.ToInt32(Year), Convert.ToInt32(thisMonth), Convert.ToInt32(Day));

            int interval = new TimeSpan(dtThis.Ticks - dtLast.Ticks).Days;