[C#] - 日期計算之今天的7天前

Convert.ToDateTime(DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek - 7) + (DateTime.Today.Date - DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek - 7)) - (DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek) - DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek - 7))).ToString("yyyyMMdd")

//此為今天的一個星期前的日期



EX:今天:2008/11/07

一個星期前:2008/10/31



為了搞這個想真久= =....