private void Navigation_Button_Click(object sender, RoutedEventArgs e)
        {
            Button button    = sender as Button;
            var    operation = button.Content.ToString();

            switch (operation)
            {
            case "Students":
                TeacherMain teacherMain = new TeacherMain(name);
                this.NavigationService.Navigate(teacherMain);
                break;

            case "Questions":
                QuestionPage questionPage = new QuestionPage(name);
                this.NavigationService.Navigate(questionPage);
                break;

            case "Exit":
                HomePage homePage = new HomePage();
                this.NavigationService.Navigate(homePage);
                break;

            default:
                break;
            }
        }
        private void Navigation_Button_Click(object sender, RoutedEventArgs e)
        {
            Button button = sender as Button;

            var operation = button.Content.ToString();

            switch (operation)
            {
            case "Questions":
                TeacherPages.QuestionPage questionPage = new TeacherPages.QuestionPage(name);
                this.NavigationService.Navigate(questionPage);
                break;

            case "Quizzes":
                TeacherPages.QuizPage quizPage = new TeacherPages.QuizPage(name);
                this.NavigationService.Navigate(quizPage);
                break;

            case "Exit":
                HomePage homePage = new HomePage();
                this.NavigationService.Navigate(homePage);
                //while (NavigationService.CanGoBack)
                //{
                //    try
                //    {
                //        NavigationService.RemoveBackEntry();
                //    }
                //    catch (Exception ex)
                //    {
                //        break;
                //    }
                //}
                break;

            default:
                break;
            }
        }