Question

I have a situation where I would like to create a 1-to-1 relationship in Entity Framework (4.2) using code first fluent configuration API, the twist is that I need to use a link/map table to do it.

Here is a diagram of my table layout.

This is what I am after …

HasOptional(x => x.FieldPerson)
    .WithOptionalPrincipal()
    .Map(map =>
             {
                 map.ToTable("user_account__field_person");
                 map.MapLeftKey("user_account_id");
                 map.MapRightKey("field_person_id");
             });

… but there doesn’t seem to be a way to do it.

The alternative is to create my 3 entities and manage them myself using joins where appropriate.

Is this even possible or is it a scenario that EF fluent API doesn’t handle?

Answer 1

I’m going to answer my own question again!

I don’t think EF code first deals with this situation because the whole concept of a link/map table suggests a many-to-many relationship.

For my particular case this is a database-first situation and I “have” to deal with these tables as I cannot change the database as this stage.

What I’ve done is use a Many-to-Many code first configuration …

HasMany(t=>t.FieldPersons)
    .WithMany(t=>t.UserAccounts)
    .Map(map =>
             {
                 map.ToTable("user_account__field_person");
                 map.MapLeftKey("user_account_id");
                 map.MapRightKey("field_person_id");
             });

… as there is nothing in my database schema to prevent me from creating a many to many relationship. If I did want that behaviour then I would simply need to add a unique constraint on each field (which EF code first doesn’t support anyway)