public SelectCompletedCoursesViewModel(ISqlData sqlData, IEventAggregator eventAggregator)
 {
     _sqlData          = sqlData;
     _eventAggregator  = eventAggregator;
     _allCourses       = new BindableCollection <CourseModel>(_sqlData.GetAllCourses());
     _completedCourses = new List <CompletedCourseModel>(_sqlData.GetAllCompletedCourses(UserName));
 }