public ActionResult Register(User model)
        {
            if (ModelState.IsValid)
            {
                var user = db.Users.Where(k => k.UserName == model.UserName);


                if (user.Count() == 0)
                {
                    //try
                    {
                        if (ModelState.IsValid)
                        {
                            using (var db1 = new ConceptMapDBContext())
                            {
                                var crypto   = new SimpleCrypto.PBKDF2();
                                var encrPass = crypto.Compute(model.Pass);

                                var systemUser = db.Users.Create();


                                systemUser.UserName = model.UserName;
                                systemUser.Pass     = encrPass;
                                systemUser.PassSalt = crypto.Salt;

                                systemUser.FullName    = model.FullName;
                                systemUser.Email       = model.Email;
                                systemUser.PhoneNumber = model.PhoneNumber;


                                db1.Users.Add(systemUser);

                                db1.SaveChanges();
                            }

                            return(RedirectToAction("Index", "TrangChu"));
                        }
                    }
                    //catch (DbEntityValidationException dbEx)
                    //{
                    //    foreach (var validationErrors in dbEx.EntityValidationErrors)
                    //    {
                    //        foreach (var validationError in validationErrors.ValidationErrors)
                    //        {
                    //            System.Diagnostics.Trace.TraceInformation("Property: {0} Error: {1}", validationError.PropertyName, validationError.ErrorMessage);
                    //        }
                    //    }
                    //}
                }
                else
                {
                    ModelState.AddModelError("", "Tên đăng nhập này đã được sử dụng !");
                }
            }

            // If we got this far, something failed, redisplay form
            return(View(model));
        }