Linq 选择昨天的日期

发布于 2024-11-01 11:16:29 字数 230 浏览 1 评论 0原文

我已经了解到：

DateTime yesterday = DateTime.Today.AddDays(-1);
YesterdaysRegistrations = db.tblForumAuthors.Where(c => c.Join_date == yesterday).Count();

肯定有记录具有昨天的加入日期，但这始终返回 0！谁能告诉我我这样做是否正确？

原文

I've got as far as this:

DateTime yesterday = DateTime.Today.AddDays(-1);
YesterdaysRegistrations = db.tblForumAuthors.Where(c => c.Join_date == yesterday).Count();

There definitely records that have the join date of yesterday, but this returns 0 all the time! Can anyone tell me if I'm doing this correctly?

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如痴如狂 2024-11-08 11:16:29

AddDays 保留小时/分钟/秒组件。您要么必须使用（如果 c.Join_date 只是日期组件）：

DateTime yesterday = DateTime.Today.AddDays(-1).Date;

否则，您将比较范围：

DateTime yesterday = DateTime.Today.AddDays(-1).Date;
DateTime yesterdayEnd = DateTime.Today.Date.AddSeconds(-1);
db.tblForumAuthors.Where(c => c.Join_date >= yesterday && c.Join_date < yesterdayEnd)

AddDays keeps the Hour/Minute/Second components. You either have to use (if c.Join_date is only the date component):

DateTime yesterday = DateTime.Today.AddDays(-1).Date;

Otherwise, you compare for range:

DateTime yesterday = DateTime.Today.AddDays(-1).Date;
DateTime yesterdayEnd = DateTime.Today.Date.AddSeconds(-1);
db.tblForumAuthors.Where(c => c.Join_date >= yesterday && c.Join_date < yesterdayEnd)

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ぇ气 2024-11-08 11:16:29

你不必削减时间，你只需要确保你没有做完全匹配的事情。

试试这个：

DateTime today = DateTime.Today; // read once, avoid "odd" errors once in a blue moon
DateTime yesterday = today.AddDays(-1);
YesterdaysRegistrations = db.tblForumAuthors.Where(
    c => c.Join_date >= yesterday
      && c.Join_date < today).Count();

You don't have to strip off the time, you just have to make sure you don't do an exact match.

Try this instead:

DateTime today = DateTime.Today; // read once, avoid "odd" errors once in a blue moon
DateTime yesterday = today.AddDays(-1);
YesterdaysRegistrations = db.tblForumAuthors.Where(
    c => c.Join_date >= yesterday
      && c.Join_date < today).Count();

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