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我有这种情况，我没有通过相关的 SO 问题找到任何解决方案：

  (from TD as tx 
   join P as px  on tx.field1= px.ID
   join Q as rp  on tx.field2 = rp.ID
   join L as lc  on tx.field3= lc.ID
    group by  tx.field1,
              tx.field2, 
              L.randomfield4,
              ....a bunch of fields from P,Q,L
   )as groupItem
   left outer join M on groupItem.field1=M.ID
   select new { */ Elements from groupItem and M /*}

我的 Linq 如下所示：

from tx in TD 
join itemP in P on tx.field1 equals P.ID
join itemQ in Q on tx.field2 equals P.ID
join itemL in L on tx.field3 equals P.ID
 group new { tx.field1 ,tx.field2 ,L.randomfield4 } by new { **fields from tx,p,q,etc} into groupItem 
 join dM in M on ????

如果我尝试从 groupItems 中选择元素，我将无法访问属性（因为我没有选择任何内容）。

任何人都可以帮助我解决这个问题吗？
也帮我为这个问题取一个更好的名字:)

4

1 回答 1

2

希望我正确理解了您的问题，但这是我的答案。我将查询分为两部分，因此如果您完全了解它，只需将它们组合在一起就很容易理解。

基本上，变量“groupedCollection”是您的第一个连接，您的分组基本上包括以下集合 TD、P、Q 和 L。然后第二个变量“finalCollection”是您的左外连接，它给出了您需要的结果。

var groupedCollection = from tx in TD
join itemP in P on tx.field1 equals itemP.ID
join itemQ in Q on tx.field2 equals itemQ.ID
join itemL in L on tx.field3 equals itemL.ID
group new
{   
    //Select the collections you want to group it by
    P,
    Q,
    L,
    TD
}
by new
{
    //Select fields you want to output group by here
    tx.field1,
    tx.field2,
    tx.field3,
    itemL.RandomField4
}
    into g
    select new
    {
        //Use ky to get your properties as they are already grouped by
        yourField1 = g.Key.field1,
        yourField2 = g.Key.field2,
        yourField3 = g.Key.field3,
        yourField4 = g.Key.RandomField4
    };

var finalCollection = from dM in M
    //This is your Left Outer Join
    join xx in groupedCollection on dM.ID equals xx.yourField1 into sr
    from w in sr.DefaultIfEmpty()
    //Until here
    select new
    {
        finalResultID = dM.ID,
        finalField1 = w.yourField1,
        finalField2 = w.yourField2,
        finalField3 = w.yourField3,
        finalField4 = w.yourField4
    };

对于更多 LINQ 的东西，这会给你一个想法 http://anyrest.wordpress.com/2010/09/27/linq-to-sql-essentials/

于 2013-02-18T22:45:00.253 回答