c# - Unable to update Foreign Key in Entity Framework 6

Question

I am trying to do a simple update to the foreign key but the script never get sent over.

Here is the code I am using:

using (var db = new MyContext())
{
      db.Entry<Contact>(newContact).State = EntityState.Modified;
      newContact.ContactOwner = db.Person.Find(3);
      db.SaveChanges();
}

EF6 update the rest of the column in the Persons table but it is not updating the Contact_Id in Persons table.

Person entity:

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public List<Contact> ContactList { get; set; }
}

Contact entity:

public class Contact
{
    public int Id { get; set; }
    public string Email { get; set; }
    public string TelNo { get; set; }
    public Person ContactOwner { get; set; }
}

What am I missing here?

Please help!

Answer 1

Since you are working with independent association. You can either

• Adding and removing the relationship from ContactList, but you need to retrieve from both Person.

  db.Entry(newContact).State = EntityState.Modified;
  
  var p1 = db.Set<Person>().Include(p => p.ContactList)
      .FirstOrDefault(p =>p.Id == 1);
  p1.ContactList.Remove(newContact);
  
  var p3 = db.Set<Person>().Include(p => p.ContactList)
      .FirstOrDefault(p => p.Id == 3);
  p3.ContactList.Add(newContact);
  
  db.SaveChanges();
  

• Or you can use disconnected object, but you need to manually manage the relationship.

  db.Entry(newContact).State = EntityState.Modified;
  
  var p1 = new Person { Id = 1 };
  db.Entry(p1).State = EntityState.Unchanged;
  var p3 = new Person { Id = 3 };
  db.Entry(p3).State = EntityState.Unchanged;
  
  var manager = ((IObjectContextAdapter)db).ObjectContext.ObjectStateManager;
  manager.ChangeRelationshipState(newContact, p1, item => item.ContactOwner,
       EntityState.Deleted);
  manager.ChangeRelationshipState(newContact, p3, item => item.ContactOwner,
       EntityState.Added);
  
  db.SaveChanges();
  

PS

You might need to reconsider adding foreign key value, to make everything easier, updating foreign key just by mentioning the Id.

See this post for more information.