如何在LINQ to Entities中执行SQL“Where存在”？

我真的想做这样的事情：

Select * from A join B on A.key = B.key join C on B.key = C.key -- propagated keys where exists (select null from B where A.key = B.key and B.Name = "Joe") and exists (select null from C where B.key = C.key and C.Name = "Kim") 

使用Entity Framework 4和C＃时，linq语句会是什么样子？

更新：

显然.Contains（）将产生“Where Exists”结果。 所以，另一种尝试
（我不知道这是否会编译LOL）：

 var inner1 = from recordB in B where recordB.Name = "Joe" select recordB.key; var inner2 = from recordC in C where recordC.Name = "Kim" select recordC.key; var result = from recordA in A where inner1.Contains( recordA.key) && inner2.Contains( recordA.key) select recordA; 

编辑：哇这是实际工作的：

 var result = from A in Products where A.kfield1 == 1 && A.kfield2 == 2 && ( from B in Btable where B.otherid == "Joe" && // field I want to select by B.kfield1 == A.kfield1 && B.kfield2 == A.kfield2 // Can keep adding keys here select A.identifier // unique identity field ).Contains(A.identifier) && ( from C in Ctable where C.otherid == "Kim" && // field I want to select by C.kfield1 == A.kfield1 && C.kfield2 == A.kfield2 // Can keep adding keys here select A.identifier // unique identity field ).Contains(A.identifier) select A; 

这产生了这个SQL：

 SELECT [t0].[identifier], [t0].* FROM [A] AS [t0] WHERE ([t0].[kfield1] = @p0) AND ([t0].[kfield2] = @p1) AND (EXISTS( SELECT NULL AS [EMPTY] FROM [B] AS [t1] WHERE ([t0].[identifier] = [t0].[identifier]) AND ([t1].[otherid] = @p2) AND ([t1].[kfield1] = [t0].[kfield1]) AND ([t1].[kfield2] = [t0].[kfield2]))) AND (EXISTS( SELECT NULL AS [EMPTY] FROM [C] AS [t2] WHERE ([t0].[identifier] = [t0].[identifier]) AND ([t2].[otherid] = @p3) AND ([t2].[kfield1] = [t0].[kfield1]) AND ([t2].[kfiekd2] = [t0].[kfield2]) )) 

这就是我想要的。 请注意[t0]。[identifier] = [t0]。[identifier]，它会过滤掉空值，因为null不会比较包含其自身的任何内容（在SQL中）

Answer 1

.Any()扩展方法通常映射到exists 。

Answer 2

您是否尝试将exists条件添加到连接中？

 from a in context.AEntity Join B in context.BEntity on A.Key equals B.Key && B.Name == "Joe" Join C in context.CEntity on B.Key equals C.Key && C.Name == "Kim"; 

不确定这是否有效，但值得一试。