LINQ的DateTime转换为字符串 [英] LINQ convert DateTime to string

问题描述

List<Post> list =
(
    from c in db.TitleComments
    join t in db.Titles on c.TitleId equals t.Id
    join u in db.Users on c.UserId equals u.Id
    where t.Id == _titleId && c.Date > time
    orderby c.Date descending
    select new Post { Username = u.Username, PostingDate = c.Date.ToString(), Data = c.Comment }
).ToList();

上面的code使上日期的皈依串例外，PostingDate = c.Date.ToString（）。任何想法如何解决这个问题？

The code above causes exception on the convertion of date to string, PostingDate = c.Date.ToString(). Any ideas how to get around this?

异常错误：
{LINQ到实体无​​法识别方法'System.String的ToString（）方法，而这种方法不能被翻译成店前pression。}

Exception error: {"LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method cannot be translated into a store expression."}

推荐答案

的 LINQ试图使用SQL日期转换为字符串，但因为是在SQL没有ToString（）方法不能将其转换，这种行为是由设计的 - 乔金 -

linq is trying to convert date to string using sql but since there is no ToString() method in sql it can't convert it, this behavior is by design - Joakim

在换句话说，返回日期本身以及它在执行SQL上偏后转换为字符串：

In other words, return the date itself and convert it to a string after it executes on SQL side:

(
select new { Username = u.Username,
    PostingDate = c.Date
    [...]
})
.ToList() // runs on SQL and returns to the application
.Select(o =>  // is not generating a SQL, it is running on the app
    new Post { Username = o.Username,
        PostingDate = o.PostingDate.ToString(),
        [...]
    })

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