在asp.net中怎么样计算两个日期相差的年月日

private double DateDiff(string howtocompare, System.DateTime startDate, System.DateTime endDate)

{

double diff=0;

System.TimeSpan TS = new System.TimeSpan(endDate.Ticks-startDate.Ticks);

switch (howtocompare.ToLower())

{

case "year":

diff = Convert.ToDouble(TS.TotalDays/365);

break;

case "month":

diff = Convert.ToDouble((TS.TotalDays/365)*12);

break;

case "day":

diff = Convert.ToDouble(TS.TotalDays);

break;

case "hour":

diff = Convert.ToDouble(TS.TotalHours);

break;

case "minute":

diff = Convert.ToDouble(TS.TotalMinutes);

break;

case "second":

diff = Convert.ToDouble(TS.TotalSeconds);

break;

}

return diff;

}