如何获取DateTimeFormatInfo.FirstDayOfWeek添加天数的实例？

Question

以下是我的简化代码：

DateTimeFormatInfo dfi = DateTimeFormatInfo.CurrentInfo;

var firstReference = dfi.FirstDayOfWeek; // Currently, this could be Monday, Saturday, or Sunday.
var secondReference = dfi.FirstDayOfWeek.AddDays(3); // For this one, it should be something like 3 days after the dynamic value of FirstDayOfWeek.

不幸的是，它不是这样工作的。那么，问题是:有没有办法获得添加了3天的dfi.FirstDayOfWeek的实例？

Answer 1

DayOfWeek是一个Enum，所以你可以将它转换成int，添加days，然后再转换回来，就像这样：

var secondReference = (DayOfWeek)(((int)dfi.FirstDayOfWeek+3)%7);

为了避免DayofWeek大于7，您需要使用mod。

Answer 2

使用

DateTimeFormatInfo dfi = DateTimeFormatInfo.CurrentInfo;

var firstReference = dfi.FirstDayOfWeek;
var secondReference = (DayOfWeek)(((int)firstReference + 3) % 7);

DayOfWeek是枚举，所以fine在它上面工作得很好。

在+3超过DayOfWeek限制的情况下使用Mod (在您的情况下是周六)。

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Answer 3

您可以在星期中的某一天迭代天..

        DateTimeFormatInfo dfi = DateTimeFormatInfo.CurrentInfo;
        List<DayOfWeek> daylist = new List<DayOfWeek>();
        int i = (int)dfi.FirstDayOfWeek;
        int addDay = 3;
        while (i <= ((int)dfi.FirstDayOfWeek + addDay) % 7)
        {
            daylist.Add((DayOfWeek)i);
            i++;
        }