EF code first - configure One-to-Zero-or-One relationship without shared PK/FK

Question

I am trying to establish a One-to-Zero-or-One relationship between two entities and I want the dependent entity to still contain its own Indentity column, instead of it being a

Answer 1

Bidirectional one-to-one relationship with explicit FK property is not supported.

So either continue using what you have now - Shared Primary Key association. Just get rid of one of the TaskId or FileId properties from Task and make the remaining a PK (EF will automatically use it as FK because that's the default EF one-to-one relationship model).

Or get rid of the FieldId property from Task and use the following fluent configuration (all is necessary):

modelBuilder.Entity<File>()
    .HasOptional(f => f.Task)
    .WithRequired(t => t.File)
    .Map(m => m.MapKey("FileId"))
    .WillCascadeOnDelete();

But I would recommend using the first approach (if there is no special reason of not doing it like existing database etc.) because it's better supported - the second includes some LEFT OUTER JOINs in SQL queries as you can see from this post EF - WithOptional - Left Outer Join?.