sql server -在3个表连接或一个表没有键关系的情况下产生c#对实体(EF)查询的问题

一直在尝试一堆东西，但不能得到任何工作的实体框架。表结构:

Device       DeviceLegacy      BillingDeviceProduct
------       ------------      --------------------
ID           DeviceID          SKU = 123
Num          LegacyID          NID
Name         LegacyUID         SID

(省略多余字段)

DeviceLegacy。DeviceID是Device.ID的外键关系。DeviceLegacy和BillingDeviceProduct在数据库中没有关系，但是如果DeviceLegacy有一个BillingDeviceProduct (SKU=123)， LegacyID将等于NID或LegacyUID将等于SID。有时这两个值会匹配。有时它们不匹配，但其中一个总是匹配的。

SQL:

select Num, Name from BillingDeviceProduct bdp
join DeviceLegacy leg on leg.LegacyUID = bdp.SID or leg.LegacyID = bdp.NID
join Device on Device.id = leg.DeviceID
where SKU = 123

当DeviceLegacy和BillingDeviceProduct两个值都不匹配时，我们有以下代码:

from device in Devices
join dlegacy in DeviceLegacies
      on device.ID equals dlegacy.DeviceID
      into dl
      from devicelegacy in dl
join bdproduct in BillingDeviceProducts
      on new { devicelegacy.LegacyID, devicelegacy.LegacyUID } equals new { LegacyID = bdproduct.NID, LegacyUID = bdproduct.SID }
      into bdp
      from deviceproduct in bdp
where deviceproduct.SKU == 123
select new { device.Num, device.Name}

from bdp in BillingDeviceProducts
where bdp.SKU = 123
from dl in DeviceLegacies.Include("Device")  
where (bdp.SID == dl.LegacyUID || dbp.NID == dl.LegacyID)
select new {
    Num = dl.Device.Num,
    Name = dl.Device.Name
}