private void ExecuteBackCommand(Object parameter)
        {
            var teacherStartView = new TeacherStartView();
            var vm = new TeacherStartViewModel();

            vm.LoadData();
            teacherStartView.DataContext = vm;
            NavigationHelper.NavigateTo(teacherStartView);
        }
        private void ExecuteBackCommand(Object parameter)
        {
            var startView      = new TeacherStartView();
            var startViewModel = new TeacherStartViewModel();

            startViewModel.LoadData();
            startView.DataContext = startViewModel;

            NavigationHelper.NavigateTo(startView);
        }