Question

I am using EntityFramework 4.1.

I have the following model:

public class User 
{
   [Key]
   public int Id { get; set; }
   public string Username { get; set; } 
   public string Password { get; set; }

   public virtual User Creator { get; set; }
   public virtual User LastEditor { get; set; }
}

When I try to generate my database I got this error:

Unable to determine the principal end of an association between the
types ‘User’ and ‘User’. The principal end of this association must be
explicitly configured using either the relationship fluent API or data
annotations.

But I also have this class:

public class Course 
{
   [Key]
   public int Id { get; set; }
   public string Name { get; set; } 

   public virtual User Creator { get; set; }
   public virtual User LastEditor { get; set; }
}

And it works ok, I have these foreign keys generated:

Creator_Id
LastEditor_Id

Do I have anything to add in my User model to make it works?

Answer 1

EF tries – by convention – to create a one-to-one relationship between User.Creator and User.LastEditor because they both refer to the User class where they are themselves located in. That’s not the case for the Course class. For Course.Creator and Course.LastEditor EF creates two one-to-many relationships to the User. To achieve the same for the properties in User you will have to configure the relationships with Fluent API:

modelBuilder.Entity<User>()
    .HasOptional(u => u.Creator)     // or HasRequired
    .WithMany();

modelBuilder.Entity<User>()
    .HasOptional(u => u.LastEditor)  // or HasRequired
    .WithMany();