/// <summary>
 /// Add Subjects to SubjectComboboxItem and to subjectList
 /// </summary>
 private void addSubjectsToList()
 {
     using (SubjectContext sc = new SubjectContext())
     {
         subjectList = sc.GetAllSubjects();
     }
     foreach (Subject item in subjectList)
     {
         SubjectComboboxItem.Add(new ComboboxItemViewModel
         {
             IsSelected = (PersonData as TeacherListItemViewData).Subjects.Any(f => f.Id == item.Id),
             Name = item.Name,
             Id = item.Id
         });
     }
 }
 /// <summary>
 /// Adds subjects from the database to SubjectViewData
 /// </summary>
 private void addSubjects()
 {
     using (SubjectContext sc = new SubjectContext())
     {
         List<Subject> allSubjects = sc.GetAllSubjects();
         foreach (Subject subject in allSubjects)
         {
             if (Ssvd.Subjects.Any(p => p.Id == subject.Id))
             {
                 if (SelectedSubject != null && SelectedSubject.Id == subject.Id)
                 {
                     Ssvd.Subjects.Remove(SelectedSubject);
                 }
                 else
                 {
                     continue;
                 }
             }
             Ssvd.Subjects.Add(new SubjectListItemViewData()
             {
                 Id = subject.Id,
                 Name = subject.Name,
             });
         }
     }
 }