如何使用LINQ to SQL处理IN子查询？

Question

我有点困惑于此.基本上我想在LINQ to SQL中执行类似以下SQL查询的操作:

SELECT f.* 
FROM Foo f
WHERE f.FooId IN (
    SELECT fb.FooId
    FROM FooBar fb
    WHERE fb.BarId = 1000
)

我们将非常感激地提供任何帮助.

谢谢.

Answer 1

在LINQ to SQL中实现IN的一般方法

var q = from t1 in table1
        let t2s = from t2 in table2
                  where <Conditions for table2>
                  select t2.KeyField
        where t2s.Contains(t1.KeyField)
        select t1;

在LINQ to SQL中实现EXISTS的一般方法

var q = from t1 in table1
        let t2s = from t2 in table2
                  where <Conditions for table2>
                  select t2.KeyField
        where t2s.Any(t1.KeyField)
        select t1;

Answer 2

看看这篇文章.基本上,如果要获得等效的IN,则需要首先构造内部查询,然后使用Contains()方法.这是我翻译的尝试:

var innerQuery = from fb in FoorBar where fb.BarId = 1000 select fb.FooId;
var result = from f in Foo where innerQuery.Contains(f.FooId) select f;