日期处理函数

1.

        #region 日期处理函数
        /// <summary> 
        /// 计算本周的周一日期 
        /// </summary> 
        /// <returns></returns> 
        private static DateTime GetMondayDate()
        {
            return GetMondayDate(DateTime.Now);
        }
        /// <summary> 
        /// 计算本周周日的日期 
        /// </summary> 
        /// <returns></returns> 
        private static DateTime GetSundayDate()
        {
            return GetSundayDate(DateTime.Now);
        }
        /// <summary> 
        /// 计算某日起始日期（礼拜一的日期） 
        /// </summary> 
        /// <param name="someDate">该周中任意一天</param> 
        /// <returns>返回礼拜一日期，后面的具体时、分、秒和传入值相等</returns> 
        private static DateTime GetMondayDate(DateTime someDate)
        {
            int i = someDate.DayOfWeek - DayOfWeek.Monday;
            if (i == -1) i = 6;// i值 > = 0 ，因为枚举原因，Sunday排在最前，此时Sunday-Monday=-1，必须+7=6。 
            TimeSpan ts = new TimeSpan(i, 0, 0, 0);
            return someDate.Subtract(ts);
        }
        /// <summary> 
        /// 计算某日起始日期（礼拜六的日期） 
        /// </summary> 
        /// <param name="someDate">该周中任意一天</param> 
        /// <returns>返回礼拜一日期，后面的具体时、分、秒和传入值相等</returns> 
        private static DateTime GetSaturdayDate(DateTime someDate)
        {
            int i = someDate.DayOfWeek - DayOfWeek.Saturday;
            if (i == -6) i = 1;// i值 > = 0 ，因为枚举原因，Sunday排在最前，此时Sunday-Saturday=-6，必须+7=1。 
            TimeSpan ts = new TimeSpan(i, 0, 0, 0);
            return someDate.Subtract(ts);
        }
        /// <summary> 
        /// 计算某日结束日期（礼拜日的日期） 
        /// </summary> 
        /// <param name="someDate">该周中任意一天</param> 
        /// <returns>返回礼拜日日期，后面的具体时、分、秒和传入值相等</returns> 
        private static DateTime GetSundayDate(DateTime someDate)
        {
            int i = someDate.DayOfWeek - DayOfWeek.Sunday;
            if (i != 0) i = 7 - i;// 因为枚举原因，Sunday排在最前，相减间隔要被7减。 
            TimeSpan ts = new TimeSpan(i, 0, 0, 0);
            return someDate.Add(ts);
        }
        /// <summary>
        /// 取得某月的第一天
        /// </summary>
        /// <param name="datetime">该月的任意一天</param>
        /// <returns></returns>
        private static DateTime FirstDayOfMonth(DateTime datetime)
        {
            return datetime.AddDays(1 - datetime.Day);
        }

        //// <summary>
        /// 取得某月的最后一天
        /// </summary>
        /// <param name="datetime">该月的任意一天</param>
        /// <returns></returns>
        private static DateTime LastDayOfMonth(DateTime datetime)
        {
            return datetime.AddDays(1 - datetime.Day).AddMonths(1).AddDays(-1);
        }
        /// <summary>
        /// 取得某月的所有周末日期
        /// </summary>
        /// <param name="datetime">该月的任意一天</param>
        /// <returns></returns>
        private static List<DateTime> WeekendOfMonth(DateTime datetime)
        {
            List<DateTime> weekenList = new List<DateTime>();
            DateTime fM = FirstDayOfMonth(datetime);
            DateTime lM = LastDayOfMonth(datetime);
            int length = lM.Day;
            for (int i = 0; i <= length; i++)
            {
                if (fM.AddDays(i) <= lM && (fM.DayOfWeek == DayOfWeek.Saturday || fM.DayOfWeek == DayOfWeek.Sunday))
                {
                    weekenList.Add(fM);
                }
            }
            return weekenList;    
        }
        #endregion