C# 获取某月的第一天和最后一天

/// <summary> /// 取得某月的第一天 /// </summary> /// <param name="datetime">要取得月份第一天的时间</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时间</param> /// <returns></returns> private DateTime LastDayOfMonth(DateTime datetime) { return datetime.AddDays(1 - datetime.Day).AddMonths(1).AddDays(-1); } <summary> /// 取得上个月第一天 /// </summary> /// <param name="datetime">要取得上个月第一天的当前时间</param> /// <returns></returns> private DateTime FirstDayOfPreviousMonth(DateTime datetime) { return datetime.AddDays(1 - datetime.Day).AddMonths(-1); } <summary> /// 取得上个月的最后一天 /// </summary> /// <param name="datetime">要取得上个月最后一天的当前时间</param> /// <returns></returns> private DateTime LastDayOfPrdviousMonth(DateTime datetime) { return datetime.AddDays(1 - datetime.Day).AddDays(-1); }