public void ClearDisplayData()
 {
     QualificationList.Clear();
     QualificationOpeningList.Clear();
     QualificationCertificateList.Clear();
     QualificationPrerequisitesList.Clear();
 }
        private void DisplayPrerequisites(string qualificationId)
        {
            QualificationPrerequisitesList.Clear();

            var courses = PrerequisiteService.GetQualificationPrerequisites(qualificationId)
                          .Select(c => new QualificationPrerequisitesViewModel(c));

            foreach (var course in courses)
            {
                QualificationPrerequisitesList.Add(course);
            }
        }