sql - 为什么EF查询引用属性时会生成这个sql

Question

使用 AdventureWorks 数据库并发出此查询时:

   AdventureWorksEntities entities = new AdventureWorksEntities();
   entities.Contacts.Where(x => x.FirstName == "A" 
                               || x.FirstName == "B" 
                               || x.FirstName == "C")
                     .ToList();

将被翻译成这个sql，这是它所能做到的最好的:

//ommited for brevity
FROM [Person].[Contact] AS [Extent1]
WHERE [Extent1].[FirstName] IN (N'A',N'B',N'C')

但是，当我发出此查询时:

entities.Employee.Where(x => x.Contact.FirstName == "A" 
                             || x.Contact.FirstName == "B" 
                             || x.Contact.FirstName == "C")
                .ToList();

我得到这个 SQL:

//ommited for brevity
FROM   [HumanResources].[Employee] AS [Extent1]
INNER JOIN [Person].[Contact] AS [Extent2] ON [Extent1].[ContactID] = [Extent2].[ContactID]
LEFT OUTER JOIN [Person].[Contact] AS [Extent3] ON [Extent1].[ContactID] = [Extent3].[ContactID]
WHERE [Extent2].[FirstName] = N'A' OR [Extent3].[FirstName] IN (N'B',N'C')

为什么我会得到内部和外部联接，并且 EF 是否将它们拆分为 where ？

注意使用 contains 创建相同的 SQL:

var names = new List<string>{"A", "B", "C"};
entities.Employee.Where(x => names.Contains(x.Contact.FirstName)).ToList();

编辑:所以它似乎是一个 EF 错误，我已经接受了提供解决方法的答案

编辑:打开连接问题，它位于 here

Answer 1

编写一个接受 TVP 作为输入参数的存储过程，并让 EF 实现来自 SP 的结果:)