EF核心 - 条件关系 - 垂直表分裂

Question

I've to deal with a special relationship, due to an existing database schema. The db: - table Cat (id, name) - table Dog (id, name) - view Animals:

SELECT 'C' + CAST(Id AS VARCHAR) AS AnimalId, Id AS OriginalId, Name, 1 AS AnimalType 
FROM Cat
UNION
SELECT 'D' + CAST(Id AS VARCHAR) AS AnimalId, Id AS OriginalId, Name, 2 AS AnimalType 
FROM Dog

• table Consult (AnimalId, Date)

Now I need to navigate to a Cat, from my Consult-entity. I've define four entities:

1. Cat
2. Dog
3. Animal
4. Consult

The relation Consult-Animal is no problem. But I need to get the Cat when AnimalType = 2.

What I'm trying to do is something like:

modelBuilder.Entity<Cat>()
    .HasOne(a => a.Animal)
    .WithOne(a => a.Cat)
    .HasForeignKey<Cat>(k => k.Id)
    .HasPrincipalKey<Animal>(pk => pk.OriginalId && pk.AnimalType == 1);

The SQL-join should be something like this:

SELECT Animal.*, Cat.*
FROM Animal LEFT JOIN 
    Cat ON (Animal.OriginalId = Cat.Id AND Animal.AnimalType = 1)

Any ideas how to achieve this?

Answer 1

You can do the join like this

from a in context.Animal
join c in context.Cat
on new {a.OriginalId, a.AnimalType} equals {c.Id, 1}
select new {a, c}