private void TambahData() { if (tbUserID.Text != "" || tbPassword.Text != "") { try { // ini kodenya, yg catch buat tahu salahnya apa using (var db = new DBUserModel()) { UserDB newUser = new UserDB { userID = tbUserID.Text, password = tbPassword.Text }; db.UserDBs.Add(newUser); db.SaveChanges(); MessageBox.Show("User successfully added"); Close(); } } catch (DbEntityValidationException ex) { // Retrieve the error messages as a list of strings. var errorMessages = ex.EntityValidationErrors .SelectMany(x => x.ValidationErrors) .Select(x => x.ErrorMessage); // Join the list to a single string. var fullErrorMessage = string.Join("; ", errorMessages); // Combine the original exception message with the new one. var exceptionMessage = string.Concat(ex.Message, " The validation errors are: ", fullErrorMessage); // Throw a new DbEntityValidationException with the improved exception message. throw new DbEntityValidationException(exceptionMessage, ex.EntityValidationErrors); } } }