如何使用ToShortDateString在LINQ lambda表达式？ [英] How to use ToShortDateString in linq lambda expression?

问题描述

我需要调用ToShortDateString在LINQ查询起诉lambda表达式：

I need to call ToShortDateString in a linq query suing lambda expressions:

toRet.Notification = Repositories
    .portalDb.portal_notifications.OrderByDescending(p =>       p.id)
    .FirstOrDefault(p => p.date.ToShortDateString() == shortDateString);

但我得到的错误：

but I get the error:

System.NotSupportedException类型的异常出现在
System.Data.Entity.dll但在用户代码中没有处理

An exception of type 'System.NotSupportedException' occurred in System.Data.Entity.dll but was not handled in user code

其他信息：LINQ实体无法识别方法
位System.String ToShortDateString（）'方法，和这种方法不能为
转换成店铺表达

Additional information: LINQ to Entities does not recognize the method 'System.String ToShortDateString()' method, and this method cannot be translated into a store expression.

我能做些什么，考虑到我确实需要使用 ToShortDateString（）？

What can I do, considering that I do need to use ToShortDateString() ?

感谢。

推荐答案

您不应该强迫字符串比较时，你的工作是什么同是日期/时间数据 - 只要你逼字符串比较，你会突然有应对的如何的字符串格式化

You shouldn't be forcing a string comparison when what you're working with is Date/time data - as soon as you force string comparisons, you're suddenly having to deal with how the strings are formatted.

相反，碰到这样的：

var endDate = targetDate.AddDays(1);

toRet.Notification = Repositories
.portalDb.portal_notifications.OrderByDescending(p =>       p.id)
.FirstOrDefault(p => p.date >= targetDate && p.date < endDate);

（假设 targetDate 是什么的DateTime 变量，你必须被用来制作 shortDateString 在你的代码，并且已经是日期时间没有时间值）

(Assuming that targetDate is whatever DateTime variable you had that was used to produce shortDateString in your code, and is already a DateTime with no time value)

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