private void btnCalculate_Click(object sender, RoutedEventArgs e) { orderViewModel.CalculateAmountSaveExecute(); if (orderViewModel.TotalAmount > 0) { DataGridResults.IsEnabled = false; cmbSize.IsEnabled = false; isValidSize = false; isValidChecked = false; } else { DataGridResults.IsEnabled = true; cmbSize.IsEditable = true; } IsCalculatingEnabled(); }