Entity Framework ModelBinding

I've been struggling with this problem for quite some time now. I just can't seem to get my entity objects to update correctly when using UpdateModel().

I just don't see this as a complex data model. It seems like this should be a very common situation. Perhaps there is something I need to add in the context for the fluent api to elminate this error, but I can't figure it out for the life of me.

ERROR MESSAGE

The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.

Here are my models and context:

Contact:

public class Contact {
    public Contact() {
      this.ContactInformations = new HashSet<ContactInformation>();
    }
    public int ContactId { get; set; }
    [Required]
    public string Firstname { get; set; }
    [Required]
    public string Lastname { get; set; }
    public virtual ICollection<ContactInformation> ContactInformations { get; set; }
  }

ContactInformation:

public class ContactInformation {
    public int Conta开发者_如何学PythonctInformationId { get; set; }
    public int ContactTypeId { get; set; }
    public int ContactId { get; set; }
    [Required]
    public string Information { get; set; }
}

DatabaseContext:

public class Database : DbContext {

    public Database()
      : base("Contacts") {
    }

    public DbSet<Contact> Contacts { get; set; }
    public DbSet<ContactInformation> ContactInformations { get; set; }
}

Contact Controller.

    public ActionResult Edit(int id, Contact form) {
      var contact = db.Contacts.SingleOrDefault(c => c.ContactId == id);
      UpdateModel(contact);
      db.SaveChanges();
      return RedirectToAction("Index");
}

FORM DATA

[0] "ContactId"  
[1] "Firstname"    
[2] "Lastname"   
[3] "ContactInformations[0].Index" 
[4] "ContactInformations[0].ContactInformationId" 
[5] "ContactInformations[0].ContactId"    
[6] "ContactInformations[0].Information"    
[7] "ContactInformations[0].ContactTypeId"
[8] "ContactInformations[1].Index" 
[9] "ContactInformations[1].ContactInformationId" 
[10] "ContactInformations[1].ContactId"    
[11] "ContactInformations[1].Information"    
[12] "ContactInformations[1].ContactTypeId"

UPDATE related issue with some interesting details to my problem Here

---

Relationships in EF are first-class entities. So when you break this connection you must (1) remove the relationship and (2) delete the entity. In this code:

  foreach (var item in needDeleted) {
    //have to use the datacontext directly.  I desperately want this gone!
    db.ContactInformations.Remove(db.ContactInformations.Single(c => c.ContactInformationId == item.ContactInformationId));

    //This will produce the same error as UpdateModel(contact)
    //contact.ContactInformations.Remove(contact.ContactInformations.SingleOrDefault(c => c.ContactInformationId == item.ContactInformationId));
  }

... you do (1) but not (2).

You could do:

  foreach (var item in needDeleted) {
    var ci = contact.ContactInformations.Single(c => c.ContactInformationId == item.ContactInformationId);
    contact.ContactInformations.Remove(ci); // 1
    db.ContactInformations.Remove(ci);      // 2
  }

However, the more common way is to put a cascade on the FK and surface that in your model. In which case (1) will work by itself.