private void OpenChangeSubjectDialog_Execute()
 {
     View = new SubjectView();
     View.Window.Closing += UpdateChangeSubject;
     View.ShowView(new SubjectViewViewModel(SelectedSubject));
 }
 private void OpenAddSubjectDialog_Execute()
 {
     View = new SubjectView();
     View.Window.Closing += ClosingSubjectDialog;
     View.ShowView(new SubjectViewViewModel(Subjects));
 }