Linq组加入和where连接表的属性声明 [英] Linq group join and where statement on property of the joined table

问题描述

所以我相信我已经发现， group join 是一个左外连接，这就是我需要的。但是，我需要检查连接的表属性是否为 null 。但是我还没有工作。

So I believe I have found out that group join is a left outer join and that is what I need. But I need to check if the joined tables property is null. But I haven't got it working yet.

所以我基本上需要在Linq实体框架中相当于这个查询

So I basically need the equivalent of this query in Linq Entity Framework

SELECT
    id, test, test2 
FROM Table1 
LEFT OUTER JOIN Table2 ON 
    table1.id = table2.id 
WHERE table2.example = NULL;

我已经尝试用lambda这样做，但没有任何成功。我似乎无法获取 table2 属性示例的其中语句。

I have tried to do this with lambda but without any success yet. I can't seem to get the hold of the table2 property example for the where statement.

推荐答案

您可以使用LINQ扩展方法（GroupJoin）来流览此示例：

You can flow this example using LINQ Extension Method (GroupJoin):

    Table1.GroupJoin(Table2,
                    x => x.ID,
                    y => y.ID,
                    (tbl1, tbl2) => new {Table1=tbl1, Table2 =tbl2.DefaultIfEmpty()})
                    .SelectMany(
                    tbl => tbl.Table2.Where(t2 => t2.example == null).Select(x => new
                    {
                        id= tbl.Table1.ID,
                        test = tbl.Table1.Test,
                        test2 = tbl.Table2.Test
                    }))ToList();

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