EF 5.0 code first navigation property - entity-framework

Question

I have got a User entity there are my users are stored in. For some users (admins) I would like to add additional details.
I have written following code.
public partial class UserProfile
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int UserId { get; set; }
[Display(Name = "EMail")]
[Required]
public string UserName { get; set; }
[ForeignKey("AdminDetailID")]
public virtual AdminDetail AdminDetail { get; set; }
public int? AdminDetailID { get; set; }
}
public class AdminDetail
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int AdminDetailID { get; set; }
[ForeignKey("UserId")]
public virtual UserProfile UserProfile { get; set; }
public int UserId { get; set; }
}
I like to navigate from my AdminDetail table back to my User Profile table by writing eg. admin.UserProfile.UserName. However, when I run Database-Update I receive:
The principal end of this association must be explicitly configured using either the relationship fluent API or data annotations.
When I delete the UserProfile property everything works great.. How can I create a "back" navigation within my AdminDetail class?

Answer 1

Entity Framework Code-First allows for polymorphic classes to be stored in the same table. Have you considered using a relationship like this instead?
public partial class UserProfile
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int UserId { get; set; }
[Display(Name = "EMail")]
[Required]
public string UserName { get; set; }
}
public class AdminProfile : UserProfile
{
// AdminProfile members.
}
This results in a UserProfile table with an additional column called Discriminator that EF creates and manages for you. This column indicates whether each row in the table is a UserProfile or an AdminProfile. Rows which are of type UserProfile ignore the columns that are specific to AdminProfile when accessed by EF.
Entity framework handles all of the type discrimination for you so you don't need to worry about that directly. Your DbContext will simply have a DbSet which can also store entities of type AdminProfile.

Answer 2

You don't need to have a FK in your UserProfile class. To set up a proper 1:1 only the AdminDetail class would actually need to have the foreign key to the UserProfile class. You can still keep the virtual property to be able to navigate back and forth, and EF will know what it is that you're doing. Similar to this:
public partial class UserProfile
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int UserId { get; set; }
[Display(Name = "EMail")]
[Required]
public string UserName { get; set; }
public virtual AdminDetail AdminDetail { get; set; }
}