Multiple one to many relationships with Entity Framework

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?

Take a look at this question and see if it leads you in the right direction: http://stackoverflow.com/questions/6531671/what-does-principal-end-of-an-association-means-in-11-relationship-in-entity-fr — Cyric297, Jun 14 '12 at 16:03

Slauma · Accepted Answer · 2012-06-14T16:26:43.133

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();

Multiple one to many relationships with Entity Framework

1 Answers1