private void AddEvent(object sender, EventArgs e) { Title = _titleEntry.Text; Author = _authorEntry.Text; Rating = _ratingEntry.Text; var isWrong = !int.TryParse(Rating, out var parsed) || parsed > 10; if (Title.Length == 0) { MessageDialogDisplayer.Show(this, "Title cannot be empty!"); return; } if (Author.Length == 0) { MessageDialogDisplayer.Show(this, "Author cannot be empty!"); return; } if (!Rating.All(char.IsDigit) || isWrong) { MessageDialogDisplayer.Show(this, "Wrong format for score!"); return; } if (_formatBox.Active == -1) { MessageDialogDisplayer.Show(this, "Format cannot be empty!"); return; } //gets the active item out of the combobox _formatBox.GetActiveIter(out var iterator); Format = (string)_formatBox.Model.GetValue(iterator, 0); Respond(ResponseType.Ok); Dispose(); }