Linq用子查询分组 [英] Linq group by with a sub query

问题描述

我有一个包含以下三个属性的对象:ID，DATE和NAME，并希望使用linq查询它，其结果与下面的sql语句中编写的结果相同.

I have an object that contains these three properties: ID, DATE and NAME and want to query it with linq yielding the same results as if written in the sql statement below.

SELECT ID, MAX(DATE), NAME 
FROM TABLE
GROUP BY ID

这是到目前为止我对linq的了解:

Here is what I have so far with linq:

var grouped = from a in table
group a by a.ID into g
select new fooObject()
{
DATE= g.Max(a => a.DATE),
NAME= g.Select(a => a.Name).ToString(),
ID= g.Select(a => a.ID)
};

在此先感谢您的帮助.

推荐答案

SELECT ID, MAX(DATE), NAME
FROM TABLE
GROUP BY ID

选择表中的"TABLE.NAME"列无效，因为它既不包含在聚合函数中也不在GROUP BY子句中.

Column 'TABLE.NAME' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

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