【摘】获取指定日期的起止年、月和周

本文以系统时间为例，只要对比较的时间点作改变，即可对特定日期获取起至年、月和周

 Period { Day, Week, Month, Year };


    /// <summary>
    /// 获取指定期间的起止日期
    /// </summary>
    /// <param name="period">期间类型</param>
    /// <param name="beginDate">开始日期</param>
    /// <param name="endDate">结束日期</param>
    public static void GetPeriod(Period period, out DateTime beginDate,
    out DateTime endDate)
    {
        int year = DateTime.Today.Year;
        int month = DateTime.Today.Month;

        switch (period)
        {
            case Period.Year: //年
                beginDate = new DateTime(year, 1, 1);
                endDate = new DateTime(year, 12, 31);
                break;

            case Period.Month: //月
                beginDate = new DateTime(year, month, 1);
                endDate = beginDate.AddMonths(1).AddDays(-1);
                break;

            case Period.Week: //周
                int week = (int)DateTime.Today.DayOfWeek;
                if (week == 0) week = 7; //周日

                beginDate = DateTime.Today.AddDays(-(week - 1));
                endDate = beginDate.AddDays(6);
                break;

            default: //日
                beginDate = DateTime.Today;
                endDate = DateTime.Today;
                break;
        }
    }

//调用示例
DateTime beginDate, endDate;
GetPeriod(Period.Year, out beginDate, out endDate);