c# - 在 C# 中获取两个日期之间的日历周数

Question

就此问题而言，我们假设用户来自美国并使用标准公历。因此，日历周从星期日开始到星期六结束。

我想做的是确定两个日期之间存在的日历周数。 2010 年 10 月就存在我的问题的一个完美示例。10 月 16 日和 10 月 31 日之间有 4 个日历周。

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1. 10 月 10 日 - 10 月 16 日
   
2. 10 月 17 日 - 10 月 23 日
   
3. 10 月 24 日 - 10 月 30 日
   
4. 10 月 31 日 - 11 月 6 日
   

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我宁愿远离任何硬编码逻辑，例如:

if (Day == DayOfWeek.Saturday && LastDayOfMonth == 31) { ... }

谁能想出一个合乎逻辑的方法来做到这一点？

更新:
感谢所有伟大的回应，经过一番考虑，这里是我使用的解决方案:

//get the start and end dates of the current pay period
DateTime currentPeriodStart = SelectedPeriod.Model.PeriodStart;
DateTime currentPeriodEnd = SelectedPeriod.Model.PeriodEnd;

//get the first sunday & last saturday span that encapsulates the current pay period
DateTime firstSunday = DayExtensions.SundayBeforePeriodStart(currentPeriodStart);
DateTime lastSaturday = DayExtensions.SaturdayAfterPeriodEnd(currentPeriodEnd);

//get the number of calendar weeks in the span
int numberOfCalendarWeeks = DayExtensions.CalendarWeeks(firstSunday, lastSaturday);

下面是辅助类的方法:

    /// <summary>
    /// Get the first Sunday before the pay period start date
    /// </summary>
    /// <param name="periodStartDate">Date of the pay period start date</param>
    /// <returns></returns>
    public static DateTime SundayBeforePeriodStart(DateTime periodStartDate)
    {
        DateTime firstDayOfWeekBeforeStartDate;

        int daysBetweenStartDateAndPreviousFirstDayOfWeek = (int)periodStartDate.DayOfWeek - (int)DayOfWeek.Sunday;

        if (daysBetweenStartDateAndPreviousFirstDayOfWeek >= 0)
        {
            firstDayOfWeekBeforeStartDate = periodStartDate.AddDays(-daysBetweenStartDateAndPreviousFirstDayOfWeek);
        }
        else
        {
            firstDayOfWeekBeforeStartDate = periodStartDate.AddDays(-(daysBetweenStartDateAndPreviousFirstDayOfWeek + 7));
        }

        return firstDayOfWeekBeforeStartDate;
    }

    /// <summary>
    /// Get the first Saturday after the period end date
    /// </summary>
    /// <param name="periodEndDate">Date of the pay period end date</param>
    /// <returns></returns>
    public static DateTime SaturdayAfterPeriodEnd(DateTime periodEndDate)
    {
        DateTime lastDayOfWeekAfterEndDate;

        int daysBetweenEndDateAndFollowingLastDayOfWeek = (int)DayOfWeek.Saturday - (int)periodEndDate.DayOfWeek;

        if (daysBetweenEndDateAndFollowingLastDayOfWeek >= 0)
        {
            lastDayOfWeekAfterEndDate = periodEndDate.AddDays(daysBetweenEndDateAndFollowingLastDayOfWeek);
        }
        else
        {
            lastDayOfWeekAfterEndDate = periodEndDate.AddDays(daysBetweenEndDateAndFollowingLastDayOfWeek + 7);
        }

        return lastDayOfWeekAfterEndDate;
    }

    /// <summary>
    /// Get the calendar weeks between 2 dates
    /// </summary>
    /// <param name="d1">First day of date span</param>
    /// <param name="d2">Last day of date span</param>
    /// <returns></returns>
    public static int CalendarWeeks(DateTime d1, DateTime d2)
    {
        return 1 + (int)((d2 - d1).TotalDays / 7);
    }

如果你很好奇，这就是我最终对日期所做的事情:

//create an array of all the sundays in this span
DateTime[] _sundays = new DateTime[numberOfCalendarWeeks];

//put the first sunday in the period
_sundays[0] = firstSunday;

//step through each week and get each sunday until you reach the last saturday
for (int i = 1; i <= numberOfCalendarWeeks - 1; i++)
{
     DateTime d = new DateTime();
     d = firstSunday.AddDays(i * 7);
      _sundays[i] = d;
}

for (int i = 0; i <= _sundays.Length-1; i++)
{
      //bind my view model with each sunday.
}

Answer 1

这是一个通用的解决方案，我认为它应该适用于任何选择的一周开始和结束日期。您可以根据您的情况对其进行简化，但此代码使您可以选择在必要时更改一周的开始和结束时间(例如，更改为周一至周日)。在薪资申请中更改日历周的定义并不少见。

        DateTime periodStart = new DateTime(2010, 10, 17);
        DateTime periodEnd = new DateTime(2010, 11, 14);

        const DayOfWeek FIRST_DAY_OF_WEEK = DayOfWeek.Monday;
        const DayOfWeek LAST_DAY_OF_WEEK = DayOfWeek.Sunday;
        const int DAYS_IN_WEEK = 7;

        DateTime firstDayOfWeekBeforeStartDate;
        int daysBetweenStartDateAndPreviousFirstDayOfWeek = (int)periodStart.DayOfWeek - (int)FIRST_DAY_OF_WEEK;
        if (daysBetweenStartDateAndPreviousFirstDayOfWeek >= 0)
        {
            firstDayOfWeekBeforeStartDate = periodStart.AddDays(-daysBetweenStartDateAndPreviousFirstDayOfWeek);
        }
        else
        {
            firstDayOfWeekBeforeStartDate = periodStart.AddDays(-(daysBetweenStartDateAndPreviousFirstDayOfWeek + DAYS_IN_WEEK));
        }

        DateTime lastDayOfWeekAfterEndDate;
        int daysBetweenEndDateAndFollowingLastDayOfWeek = (int)LAST_DAY_OF_WEEK - (int)periodEnd.DayOfWeek;
        if (daysBetweenEndDateAndFollowingLastDayOfWeek >= 0)
        {
            lastDayOfWeekAfterEndDate = periodEnd.AddDays(daysBetweenEndDateAndFollowingLastDayOfWeek);
        }
        else
        {
            lastDayOfWeekAfterEndDate = periodEnd.AddDays(daysBetweenEndDateAndFollowingLastDayOfWeek + DAYS_IN_WEEK);
        }

        int calendarWeeks = 1 + (int)((lastDayOfWeekAfterEndDate - firstDayOfWeekBeforeStartDate).TotalDays / DAYS_IN_WEEK);