Vb.net 实体框架左连接两个数据库

我需要使用实体框架将列表连接到数据库查询。 基本上，我有两个数据库，需要将一个表从一个数据库外部连接到另一个数据库中的表。 为了做到这一点，我考虑从数据库1中获取一个列表，然后将其左键连接到第二个查询的查询。 问题是，我必须将结果作为IQueryable返回，因此方法的使用者可以在执行查询之前对查询进行额外的过滤

我尝试了两种不同的方法：

备选案文1：

 Public Shared Function List() As IQueryable(Of ContractEquipment)
' Get Subcontractors from Database 1
Dim subcontractors As List(Of SubContractor) = GetSubContractorList().ToList()
' Query Database 2
Return (From c In DB.ContractEquipments
        Select New With {
            .ContractID = c.ContractID,
            .EquipmentID = c.EquipmentID,
            .Inactive = c.Inactive,
            .SubContractorName = (From x In subcontractors Where c.SubContractorID = x.SubContractorID Select x.Name).FirstOrDefault()
        }) 

端函数

备选案文2：

Public Shared Function List() As IQueryable(Of ContractEquipment)
' Get Subcontractors from Database 1
Dim subcontractors As List(Of SubContractor) = GetSubContractorList().ToList()
' Query Database 2
Return (From c In DB.ContractEquipments
        Group Join s in subcontractors on c.SubContractorID equals s.SubContractorID into tblSubContractors = Group
        Select New With {
            .ContractID = c.ContractID,
            .EquipmentID = c.EquipmentID,
            .Inactive = c.Inactive,
            .SubContractorName = tblSubContractors.Select(Function(z) z.Name).FirstOrDefault()
        })

端函数

我总是会遇到同样的错误： 无法创建类型为的常量值。此上下文中仅支持基元类型（'如Int32、String和Guid'）

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有人有什么建议吗？

好的，我找到了解决办法。 在数据库2中创建了一个视图：

CREATE VIEW dbo.ViewContractEquipment
AS SELECT e.ContractEquipmentID, s.Name as SubContractorName
FROM dbo.ContractEquipments AS e 
LEFT OUTER JOIN DB2.dbo.SubContractors AS s ON e.SubContractorID = s.SubContractorID

然后，我将视图添加到查询中，并将其与主表联接：

    Return (From d In DB.ViewContractEquipments
        Join c in DB.ContractEquipments ON c.ContractEquipmentID equals d.ContractEquipmentID
        Select New With {
            .ContractID = c.ContractID,
            .EquipmentID = c.EquipmentID,
            .Inactive = c.Inactive,
            .SubContractorName = d.SubContractorName
        })

不优雅，但它的工作