C#獲取每月最后一天或者最末一天的方法

/// <summary>
        /// 取得某月的第一天
        /// </summary>
        /// <param name="datetime">要取得月份第一天的時間</param>
        /// <returns></returns>
        private DateTime FirstDayOfMonth(DateTime datetime)
        {
            return datetime.AddDays(1 - datetime.Day);
        }

        //// <summary>
        /// 取得某月的最后一天
        /// </summary>
        /// <param name="datetime">要取得月份最后一天的時間</param>
        /// <returns></returns>
        private DateTime LastDayOfMonth(DateTime datetime)
        {
            return datetime.AddDays(1 - datetime.Day).AddMonths(1).AddDays(-1);
        }

        //// <summary>
        /// 取得上個月第一天
        /// </summary>
        /// <param name="datetime">要取得上個月第一天的當前時間</param>
        /// <returns></returns>
        private DateTime FirstDayOfPreviousMonth(DateTime datetime)
        {
            return datetime.AddDays(1 - datetime.Day).AddMonths(-1);
        }

        //// <summary>
        /// 取得上個月的最后一天
         /// </summary>
        /// <param name="datetime">要取得上個月最后一天的當前時間</param>
        /// <returns></returns>
        private DateTime LastDayOfPrdviousMonth(DateTime datetime)
        {
            return datetime.AddDays(1 - datetime.Day).AddDays(-1);
        }

為了方便我后面找，就發布到自己下面了

轉自https://www.cnblogs.com/junjie94wan/archive/2012/08/31/2664947.html