Entity Framework 4.1 Code First Foreign Key Id's

Question

I have two entities referenced one to many. When entity framework created the table it creates two foreign keys, one for the key I have specified with the fluent interface and t

Answer 1

The default Code First conventions detect your DepartmentId foreign key, since it is, well, conventional. I think you should remove the Fluent definition:

modelBuilder.Entity<Person>()
    .HasRequired(p => p.Department)
    .WithMany()
    .WillCascadeOnDelete(false);

Answer 2

best thing is to remove departmentid property from Person class and add the following statement. MapKey will create foreign key column with the name you specify

 modelBuilder.Entity<Person>().HasRequired(p =>  p.Department)
    .WithMany().Map(x=>x.MapKey("DepartmentId"))
    .WillCascadeOnDelete(false);

Answer 3

You must specify the many-end of the association explicitely:

modelBuilder.Entity<Person>()
    .HasRequired(p => p.Department)
    .WithMany(d => d.People)
    .HasForeignKey(p => p.DepartmentId)
    .WillCascadeOnDelete(false);

Otherwise EF will assume that there are two associations: One which is not exposed in Department with the foreign key DepartmentId and navigation property Department in the Person class as you have defined in the Fluent code - and another association which belongs to the exposed navigation property People but with another not exposed end in Person and a foreign key automatically created by EF. That's the other key you see in the database.