C# (CSharp) Chosen.Count примеры использования

Пример #1

 private void UpdateCourseList(ObservableCollection <Course> action)
 {
     NumCourses = Chosen.Count().ToString();
 }

Пример #2

 private void RemoveFromCourseList(Course action)
 {
     NumCourses = Chosen.Count() + "";
 }