One-To-One relationship with fluent api. A Hacky way? - entity-framework

Question

EF 4.3.1. I have defined User and Box entities. Each box may or may not be assigned to a user.
What I'd like to achieve is to have a OwnBox property in User class, and an Owner property in Box class.
in Database, I have defined OwnerId foreignkey in Boxes (Boxes.OwnerId has relation with Users.UserId).
To define the relationship with fluent api, I have defined the following classes:
public partial class User
{
public int UserId {get; set;}
public virtual Box OwnBox { get; set; }
}
public partial class Box
{
public int? OwnerId { get; set; }
public virtual User User { get; set; }
}
Then in my Mapping class for Box, I have defined the relations as follows:
this.HasOptional(t => t.User).WithOptionalDependent(d => d.OwnBox).
Map(m => m.MapKey("OwnerId")).WillCascadeOnDelete(true);
But by firing up the project, I got the error:
Schema specified is not valid. Errors: (56,6) : error 0019: Each
property name in a type must be unique. Property name 'OwnerId' was
already defined.
So I had to tell EF to forget about the OwnerId column first:
this.Ignore(t => t.OwnerId);
Now the project works fine. But I'm still doubtful if this is a good approach and will everything work fine on CRUD operations with foreign key associations.

Answer 1

First of all, this is not one-to-one relationship. In one-to-one relationship the foreign key must be a primary key.
I believe in your scenario the situation can happen:
User = { UserID = 2 }
Box1 = { UserID = 2 }
Box2 = { UserID = 2 }
Nothing stops you from doing that, but which box should be returned when you do that:
User.OwnBox, Box1 or Box2?
EF can deal with that using Independent Association. It will create foreign key, hidden from your POCO class. You can specify the name of the column using MapKey as you did. However, because you also created a property called OnwerID, just as the column used with MapKey, the EF has a problem as two properties are mapped to the same column.
When you use ignore, the POCO OwnerID property is ignored by EF so that fixes the problem of two properties, however, the OwnderID value never gets saved or read to the database. Because EF just ignores it.
Thanks for your question, I have learnt a lot thanks to this.