public ObservableCollection <LessonModel> GetListLesson(TabName tabname) { ObservableCollection <LessonModel> result = null; result = new ObservableCollection <LessonModel>(CommonDAO.GetListLesson(tabname)); foreach (LessonModel lesson in result) { if (string.IsNullOrEmpty(lesson.LastLearning)) { lesson.IsSelected = true; break; } } return(result); }