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));
}