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