An Object with the same key already exists in the Objectstatemanager. The Objectstatemanager cannot track Multiple Objects with the same key

Question

Guys I’m having a bit of a problem, I’m trying to do an update using the Entity Framework, but when it arrives in Savechanges(), the following error appears.

An Object with the same key already exists in the Objectstatemanager. The Objectstatemanager cannot track Multiple Objects with the same key.

From what I found on the internet has something to do with the instance of my context, I tried to make a new instance but it still didn’t work.

Follows the code:

        [HttpPost]
    public ActionResult EditPassword([Bind(Include = "intIDUsuario,strNome,strUsuario,strSenha,bitStatus,strTelefone,strEmail,intIDPerfil,NovaSenha,ConfirmaSenha")] Usuario usuario)
    {
        try
        {

            var query2 = from q in db.Usuario where q.intIDUsuario == usuario.intIDUsuario select q.intIDUsuario;
            int id1 = query2.FirstOrDefault();


            string pass = Cryptography.Encrypt(usuario.strSenha);

            var user = db.Usuario.ToList().Where(x => x.strSenha == pass && usuario.NovaSenha == usuario.ConfirmaSenha).Count() > 0;

            if (user)
            {

                usuario.strSenha = Cryptography.Encrypt(usuario.NovaSenha);

                db.Entry(usuario).State = EntityState.Modified;
                db.SaveChanges();

                return RedirectToAction("Index","Suporte");
            }

            return RedirectToAction("Index", "Suporte");

        }
        catch
        {

            ModelState.AddModelError("","Ocorreu um erro!!!");

        }

        return View(usuario);
    }

Answer 1

This is because you are selecting the user several times. By default, the Entity Framework monitors all loaded objects, even if there is no change in them.

To prevent read-only objects from being monitored, use the following:

        var query2 = from q in db.Usuario where q.intIDUsuario == usuario.intIDUsuario;
        int id1 = query2.AsNoTracking().FirstOrDefault().Select(q => q.intIDUsuario);

        string pass = Cryptography.Encrypt(usuario.strSenha);

        var user = db.Usuario.AsNoTracking().Count(x => x.strSenha == pass && usuario.NovaSenha == usuario.ConfirmaSenha) > 0;

AsNoTracking loads the "read-only mode" objects. By making these changes, your code should work normally.