取得某月和上个月第一天和最后一天的方法(C#)

/**//// <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);


}