Legacy code: Code First one to one or zero relationship

Question

I have following legacy code fragment that I can't change:

public class EntityA
{
  int SeqId { get; set; }  //Not part of the key

  [Association("EntityB", "Seq_ID", "Seq_ID")]
  public EntityB EntityB { get; set; }
}

public class EntityB
{
  [Key]
  int SeqId { get; set; }
}

Database was created via SQL and not with Entity Framework. There are no foreign keys and the relation is handled as one to one/zero.

Now, we must use the model for code first and Entity Framework adds a foreign key relation. Since I can't change the model, but I can override the OnModelCreating event, I want to rewrite the relationship from required to optional. I was trying to add

modelBuilder.Entity<EntityA>().Property(i => i.EntityB).IsOptional();

and

modelBuilder.Entity<EntityA>().HasOptional(i => i.EntityB).WithOptionalDependent()

but in both cases Entity Framework complains.

Answer 1

We used following workaround:

delete the foreign key directly after creating the model. Not beautiful but effective.