private void ButtonAddCourse_Click(object sender, RoutedEventArgs e)
        {
            var courseWindow = new AddEditCourseWindow(null);

            if (courseWindow.ShowDialog() == true)
            {
                _repo.Courses.Add(courseWindow.Course);
                UpdateCourseList();
            }
        }
        private void ButtonEditCourse_Click(object sender, RoutedEventArgs e)
        {
            var selectedCourse = listBoxCourses.SelectedItem as Course;

            if (selectedCourse == null)
            {
                MessageBox.Show("Select a course from the list");
                return;
            }

            var courseWindow = new AddEditCourseWindow(selectedCourse);

            if (courseWindow.ShowDialog() == true)
            {
                UpdateCourseList();
            }
        }