public bool AddNewUser(object sender, EventArgs e, string login, string password, string passwordRepeat) { bool validationParametr = true; if (password == passwordRepeat) { string salt = RegistrationModel.CreateSalt(10); string hashpassword = RegistrationModel.GenerateSHAHash256(password, salt); List <User> users = Db.Users.ToList(); User user = new User(login, hashpassword, salt); var character = users.Find(c => c.Login == login); if (character is null) { Db.Add(user); Db.SaveChanges(); } else { validationParametr = false; string errorMessage = FormattableString.Invariant($"This login already exists"); MessageBox.Show(errorMessage); } } else { validationParametr = false; string errorMessage = FormattableString.Invariant($"Passwords do not match"); MessageBox.Show(errorMessage); } return(validationParametr); }