【轉載】對C#DateTime的一些擴充,計算周內第一天，最後一天

標籤：

    /// <summary>    /// DateTime的一些擴充    /// </summary>    public class DateTime2    {        /// <summary>        /// 得到本周第一天(以星期天為第一天)        /// </summary>        /// <param name="datetime"></param>        /// <returns></returns>        public DateTime GetWeekFirstDaySun(DateTime datetime)        {            //星期天為第一天            int weeknow = Convert.ToInt32(datetime.DayOfWeek);            int daydiff = (-1) * weeknow;            //本周第一天            string FirstDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");            return Convert.ToDateTime(FirstDay);        }        /// <summary>        /// 得到本周第一天(以星期一為第一天)        /// </summary>        /// <param name="datetime"></param>        /// <returns></returns>        public DateTime GetWeekFirstDayMon(DateTime datetime)        {            //星期一為第一天            int weeknow = Convert.ToInt32(datetime.DayOfWeek);            //因為是以星期一為第一天，所以要判斷weeknow等於0時，要向前推6天。            weeknow = (weeknow == 0 ? (7 - 1) : (weeknow - 1));            int daydiff = (-1) * weeknow;            //本周第一天            string FirstDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");            return Convert.ToDateTime(FirstDay);        }        /// <summary>        /// 得到本周最後一天(以星期六為最後一天)        /// </summary>        /// <param name="datetime"></param>        /// <returns></returns>        public DateTime GetWeekLastDaySat(DateTime datetime)        {            //星期六為最後一天            int weeknow = Convert.ToInt32(datetime.DayOfWeek);            int daydiff = (7 - weeknow) - 1;            //本周最後一天            string LastDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");            return Convert.ToDateTime(LastDay);        }        /// <summary>        /// 得到本周最後一天(以星期天為最後一天)        /// </summary>        /// <param name="datetime"></param>        /// <returns></returns>        public DateTime GetWeekLastDaySun(DateTime datetime)        {            //星期天為最後一天            int weeknow = Convert.ToInt32(datetime.DayOfWeek);            weeknow = (weeknow == 0 ? 7 : weeknow);            int daydiff = (7 - weeknow);            //本周最後一天            string LastDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");            return Convert.ToDateTime(LastDay);        }    }

原文連結：http://blog.csdn.net/joyhen/article/details/9179763

【轉載】對C#DateTime的一些擴充,計算周內第一天，最後一天