private void CoursesDisplay_SelectionChanged(object sender, SelectionChangedEventArgs e)
 {
     Status.Visibility = Visibility.Hidden;
     selectedCourse    = (Classroom.Course)e.AddedItems[0];
     this.CreateAssignments.Visibility = Visibility.Visible;
 }
 public void Add(Course course)
 {
     CourseEntries.Add(course);
 }