如何使用 DayOfWeek 获取之前的日期？

发布于 2024-12-11 20:35:10 字数 868 浏览 0 评论 0原文

我的数据库中有一个提醒表，其中有 2 列用于存储 ActionDay 和 ReminderDay。这些天数都存储为整数： 0 (sun) -> 0 (sun) -> 0 (sun) -> 6（星期六）代表一周中的几天。

当我加载页面时，我想显示下一个 ActionDay 日期以及 ReminderDay 日期。

我可以使用以下方法计算出下一个 ActionDay 日期：

public static class DateTimeExtensions
{
    public static DateTime Next(this DateTime date, DayOfWeek weekday)
    {
        return (from i in Enumerable.Range(0, 7)
                where date.AddDays(i).DayOfWeek == weekday
                select date.AddDays(i)).First();

    }
}

我在计算 ActionDay 的上一个日期时遇到一些问题。

例如，（使用今天的日期 2011 年 10 月 26 日）：如果 ActionDay 是“3”并且 ReminderDay 是“2”那么我期望行动日为“10 月 26 日星期三”，提醒日为“10 月 25 日星期二”。

如果 ActionDay 是 0 并且 ReminderDay 是 6 我期望 “10 月 30 日星期日”和“10 月 29 日星期六”

对于如何获取此提醒日期有什么建议吗？我也有兴趣知道是否有任何好的 c# 日期时间扩展/片段，因为插入其他人测试过的东西可能比在这里编写自己的东西更容易:)

谢谢，富有的

原文

I have a reminder table in my database that has 2 columns to store the ActionDay and ReminderDay. These days are both stored as integers: 0 (sun) -> 6 (sat) to represent the days of the week.

When I load my page I'd like to show the next ActionDay date and along with the ReminderDay date.

I can work out the next ActionDay date using this:

public static class DateTimeExtensions
{
    public static DateTime Next(this DateTime date, DayOfWeek weekday)
    {
        return (from i in Enumerable.Range(0, 7)
                where date.AddDays(i).DayOfWeek == weekday
                select date.AddDays(i)).First();

    }
}

I'm having some trouble working out the previous date from the ActionDay.

For example, (using today's date of 26 Oct 2011):
If the ActionDay is '3' and the ReminderDay is '2' then I expect
'Wed, 26 Oct' for the ActionDay and 'Tues, 25 Oct' for the ReminderDay.

If the ActionDay is 0 and the ReminderDay is 6 I'd expect
'Sun, 30 Oct' and 'Sat, 29 Oct'

Any suggestions on how I might be able to get this Reminder date? I'd also be interested to know if there are any good c# datetime extensions/snippets as it might be easier to plug in something that someone else has tested than writing my own here :)

Thanks,
Rich

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第几種人 2024-12-18 20:35:10

您可以计算 ActionDay 和 ReminderDay 之间的差异，然后对表示操作日的 DateTime 调用 AddDay() 函数来获取提醒日的 DateTime：

// here a stands for the number representing the action day, and r for the reminder day
// a and r are both integers from 0 to 6
int diff;
if (a >= r)
{
    diff = a - r;
}
else
{
    diff = a + 7 - r;
}

DateTime reminderDateTime = actionDateTime.AddDays(-1 * diff);

You can calculate the difference between the ActionDay and ReminderDay and then call the AddDay() function on the DateTime representing the action day to get the DateTime for reminder day:

// here a stands for the number representing the action day, and r for the reminder day
// a and r are both integers from 0 to 6
int diff;
if (a >= r)
{
    diff = a - r;
}
else
{
    diff = a + 7 - r;
}

DateTime reminderDateTime = actionDateTime.AddDays(-1 * diff);

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