private void button_Ok_Click(object sender, RoutedEventArgs e) { if (_ui_logic.CheckAmountFormValid(textBoxAmountTransaction.Text) == false) { MessageBox.Show("The number is incorrect. (It should be greater that 0.) \nTry to press <Count> button.", "Error", MessageBoxButton.OK, MessageBoxImage.Error); } else { if (ComboBox_From.SelectedItem == null) { MessageBox.Show("You should choose a bill from a combobox.", "Error", MessageBoxButton.OK, MessageBoxImage.Error); } else { if (ComboBox_To.SelectedItem == null) { MessageBox.Show("You should choose a bill from a combobox.", "Error", MessageBoxButton.OK, MessageBoxImage.Error); } else { _repo.AddHisItem_SpecialForTransaction(Convert.ToDecimal(textBoxAmountTransaction.Text), ComboBox_From.SelectedItem as String, ComboBox_To.SelectedItem as String); textBoxAmountTransaction.Clear(); ComboBox_From.SelectedItem = null; ComboBox_To.SelectedItem = null; NavigationService.Navigate(new History()); HistoryInitialised3?.Invoke(); } } } }