Question

我正在寻找一些逻辑，使用c＃让日期在下个月的第一个星期日达到给定日期。如何使用c＃获取给定日期的下个月的第一个星期日？

Answer 1

public static DateTime GetFirstSundayOfNextMonth(DateTime givenDate)
{
    DateTime firstDayNextMonth = givenDate.AddDays(-givenDate.Day + 1).AddMonths(1);
    int diff = 7 - (int)firstDayNextMonth.DayOfWeek;
    return firstDayNextMonth.AddDays(diff);
}

Answer 2

您没有显示任何工作，但让我们一步一步地编写Jon says代码;

如何获得给定日期下个月的第一个星期日

我们在您的问题中针对指定日期将dt称为DateTime。所有月份均以1作为日期编号开头。这就是为什么我们可以创建一个名为DateTime

的firstDayOfNextMonth

DateTime firstDayOfNextMonth = new DateTime(dt.Year, dt.Month + 1, 1);

现在怎样？当然我们需要检查一天的名字，它是星期天还是不。到什么时候？直到我们找到一天作为星期天。这就是为什么我们需要迭代这一天（每天 1天），直到找到它为止。我们可以使用DayOfWeek enumeration作为它的日期名称。

我们在代码中将DateTime定义为firstSundayOfNextMonth;

DateTime firstSundayOfNextMonth;

现在迭代下周的第一天，直到我们找到一个星期天;

while (firstDayOfNextMonth.DayOfWeek != DayOfWeek.Sunday)
{
    firstDayOfNextMonth = firstDayOfNextMonth.AddDays(1);
}

当这个while语句停止工作时？是的，当我们找到第一个星期天。这就是为什么我们需要将此值分配给此循环之外的firstSundayOfNextMonth变量。

while (firstDayOfNextMonth.DayOfWeek != DayOfWeek.Sunday)
{
    firstDayOfNextMonth = firstDayOfNextMonth.AddDays(1);
}

firstSundayOfNextMonth = firstDayOfNextMonth;

我们找到了它。 firstSundayOfNextMonth是给定DateTime下个月的第一个星期日（在我们的情况下为dt）。

Answer 3

试试这个：

 DateTime dt1 = new DateTime(2015, 03, 13);
 DateTime dm = dt1.AddMonths(1);
 DateTime addm = new DateTime(dm.Year,dm.Month,1);
 var nextSunday = addm.AddDays(7 - (int)addm.DayOfWeek);

您可以将2015, 03, 13替换为year,month,day。

Answer 4

为了获得某个日期之后的下一个星期，我找到了一个简单的方法。

public static DateTime FirstDayOfWeekOnOrAfter(this DateTime date, DayOfWeek dayOfWeek)
{
  return date.AddDays(Math.Abs(dayOfWeek - date.DayOfWeek));
}

public static DateTime FirstDayOfWeekOnOrBefore(this DateTime date, DayOfWeek dayOfWeek)
{
  return date.AddDays(-Math.Abs(dayOfWeek - date.DayOfWeek));
}

Answer 5

DateTime nextMonthfirstSunday;
        DayOfWeek firstDay = new DateTime(DateTime.Now.Year, DateTime.Now.Month+1, 1).DayOfWeek;
        switch (firstDay)
        {
            case DayOfWeek.Sunday:
                nextMonthfirstSunday = new DateTime(DateTime.Now.Year, DateTime.Now.Month+1, 1);
                break;
            case DayOfWeek.Monday:
                nextMonthfirstSunday = new DateTime(DateTime.Now.Year, DateTime.Now.Month + 1, 7);
                break;
            case DayOfWeek.Tuesday:
                nextMonthfirstSunday = new DateTime(DateTime.Now.Year, DateTime.Now.Month + 1, 6);
                break;
            case DayOfWeek.Wednesday:
                nextMonthfirstSunday = new DateTime(DateTime.Now.Year, DateTime.Now.Month + 1, 5);
                break;
            case DayOfWeek.Thursday:
                nextMonthfirstSunday = new DateTime(DateTime.Now.Year, DateTime.Now.Month + 1, 4);
                break;
            case DayOfWeek.Friday:
                nextMonthfirstSunday = new DateTime(DateTime.Now.Year, DateTime.Now.Month + 1, 3);
                break;
            default://Saturday
                nextMonthfirstSunday = new DateTime(DateTime.Now.Year, DateTime.Now.Month + 1, 2);
                break;
        }

Answer 6

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如何在特定日期获得下个月的第一个星期日？

6 个答案: