Question

I am trying to figure out how to make this work in EF. I have two entities Employee and User. I need to make it so the User has an optional mapping to the Employee. If there is a mapping, then it would be 1:1.

Basically this system can be accessed by employees and also by outside vendors, but I want one table to manage logons: Users.

How do I define this realtionship in EF with fluid configurations?

Answer 1

You just need to set simple fluent configuration:

modelBuilder.Entity<User>()
            .HasOptional(u => u.Employee)
            .WithRequired(e => e.User);

or in reverse order:

modelBuilder.Entity<Employee>()
            .HasRequired(e => e.User)
            .WithOptional(u => u.Employee);

EF will use Employess’s PK as FK to user – that is mandatory requirement for EF to correctly use one-to-one relation. In case of Data annotation it is enough to mark Employee’s PK with ForeignKey attribute pairing it with User navigation property:

public class Employee {
    [Key, ForeignKey("User")]
    public int Id { get; set; }

    public virtual User User { get; set; }
}