public DozierendeView(DozentViewModel viewModel)
        {
            InitializeComponent();

            this.viewModel   = viewModel;
            this.DataContext = viewModel;
        }
        public MainWindow()
        {
            InitializeComponent();

            DozentViewModel dozentViewModel = new DozentViewModel();

            UCDozierende.Content = new DozierendeView(dozentViewModel);

            StudentViewModel studentViewModel = new StudentViewModel();

            UCStudierende.Content = new StudentView(studentViewModel);
        }