有没有更有效的方法可以在C语言中得到给定日期的前一个星期一?#

所以我有一个应用程序需要有一个日期焦点,这样它才能正常运行。给定一个特定的日期来关注它需要知道它在哪一周。我正在根据星期一的日期计算星期。我想知道我对周一的关注是否过度了。

public static DateTime PreviousMonday(this DateTime dt)
{
    var dateDayOfWeek = (int)dt.DayOfWeek;
    if (dateDayOfWeek==0)
    {
        dateDayOfWeek = dateDayOfWeek + 7; 
    }
    var alterNumber = dateDayOfWeek - ((dateDayOfWeek*2)-1);

    return dt.AddDays(alterNumber);
}

/// <summary>
/// Personal tax week starts on the first Monday after the week with 6th April in unless 6th April is a Monday in 
/// which case that starts the first week. In a leap year this means you can have a week 53 which due to the mod 4 approach of calculating 
/// flexi week means you get a 5 week flexi period.
/// As such this method forces the weeks into the range 1 - 52 by finding the week number for the week containing 6th April and
/// the number for the current week. Treating the 6th April week as week 1 and using the difference to calculate the tax week.
/// </summary>
public static int GetTaxWeek(this DateTime dt)
{
    var startTaxYear = GetActualWeekNumber(new DateTime(DateTime.Now.Year, 4, 6));
    var thisWeekNumber = GetActualWeekNumber(dt);
    var difference = thisWeekNumber - startTaxYear;
    return difference < 0 ? 53 + difference : difference + 1;
}

private static int GetActualWeekNumber(DateTime dt)
{
    var ci = System.Threading.Thread.CurrentThread.CurrentCulture;
    var cal = ci.Calendar;
    var calWeekRule = ci.DateTimeFormat.CalendarWeekRule;
    var fDoW = ci.DateTimeFormat.FirstDayOfWeek;
    return cal.GetWeekOfYear(dt, calWeekRule, fDoW);
}

public static int PeriodWeek(this DateTime dt)
{
    var rawPeriodWeek = GetTaxWeek(dt) % 4;
    return rawPeriodWeek == 3 ? 1 : rawPeriodWeek + 2;
}

}

系统从第一个纳税周开始运行一个滚动的4周计划,并且需要根据计划中的位置采取不同的行为。所以你可以看到…

1. 从用户那里获取日期(比如 userDate )
2. 呼叫 userDate=userDate.PreviousMonday(); 到星期一 给定-周末在哪
3. 呼叫 userDate.PeriodWeek(); 然后得到 从1到4的时间段。

GetTaxWeek是公共的,因为它在其他地方使用…我还替换了日期,因为它被使用了不止一次,我不想记住更改它不止一次。

我能看看树林里的树吗?或者有没有一种更无错误的方法可以做到这一点。