//在ASP.NET中怎麼樣計算兩個日期相差的年、月份、日期、小時、分鐘 、秒等
//        呼叫
//        DateTime a=Convert.ToDateTime("2006-01-01 00:00");
//        DateTime b=Convert.ToDateTime("2005-01-01 00:00");
//        double d=Bll.Common.DateDiff(Bll.Common.EnumDateCompare.day,a,b);
//        Response.Write(d.ToString("f0"));//四捨五入
public enum EnumDateCompare
{
            year    =1,
            month    =2,
            day        =3,
            hour    =4,
            minute    =5,
            second    =6
}
public static double DateDiff(EnumDateCompare howtocompare, System.DateTime startDate, System.DateTime endDate)
{
            double diff=0;
            System.TimeSpan TS = new System.TimeSpan(endDate.Ticks-startDate.Ticks);

            switch (howtocompare)
            {
                case EnumDateCompare.year:
                    diff = Convert.ToDouble(TS.TotalDays/365);
                    break;
                case EnumDateCompare.month:
                    diff = Convert.ToDouble((TS.TotalDays/365)*12);
                    break;
                case EnumDateCompare.day:
                    diff = Convert.ToDouble(TS.TotalDays);
                    break;
                case EnumDateCompare.hour:
                    diff = Convert.ToDouble(TS.TotalHours);
                    break;
                case EnumDateCompare.minute:
                    diff = Convert.ToDouble(TS.TotalMinutes);
                    break;
                case EnumDateCompare.second:
                    diff = Convert.ToDouble(TS.TotalSeconds);
                    break;
            }
            return diff;
}