private void ListQuestions_SelectionChanged(object sender, SelectionChangedEventArgs e) { var selectedItem = listQuestions?.SelectedItem?.ToString(); if (string.IsNullOrWhiteSpace(selectedItem)) { return; } var result = _jsonController.FindQuestion(selectedItem); tbQuestionTitle.Text = result.Title; tblQuestionDetails.Text = result.Question; rtbShowAnswer.Document.Blocks.Clear(); rtbShowAnswer.AppendText(result.Answer); rtbShowAnswer.Visibility = Visibility.Hidden; rtbAnswerBox.Document.Blocks.Clear(); }