How do I create a 1x0..1 association in EF4 using Model-First approach?

Question

Consider the following example model:

• Person has 0..1 User
• User has 1 Person

Attempt 1:

• I dragged an association from Person to User on the model designer.
• I fixed the cardinality to meet my needs (the default is 1xN)
• I generated the DDL from model

Problem:

• The output User table has a Person_id column with no unique constraint. That is, it's not a 1x1 relationship as many Users can reference the same Person. There must be something wrong here

Attempt 2:

• Dragged an association from Person to User on the model designer.
• Fixed the cardinality to meet my needs (the default is 1xN)
• Selected the association and clicked the Referential Constraint button on the properties window to edit the association
• Selected Person to be the Principal and User to be the Dependent type
• Chosen the Principal Key to be Id and the Dependent Property to be also Id (I've read somewhere that I should use the same key for both types)

Problem:

I run this code:

using (var context = new Locadora())
{
    User user = new User ();
    user.PasswordHash = "hash";
    user.Pessoa = new Person();
    user.Pessoa.Nome = "André";

    context.Usuários.AddObject(user);

    context.SaveChanges();
}

• SaveChanges triggers this exception:

A dependent property in a ReferentialConstraint is mapped to a store-generated column. Column: 'Id'

So I am out of choices now. I don't know how to implement a 1x1 neither a 1x0..1 relationship in Entity Framework.

How do I do that?

Answer 1

The first attempt can't work because current EF version doesn't support Unique keys at all. Second approach doesn't work because you dependent entity can't have autogenerated key = StoreGeneratedPattern must be set to None .