private void changeBtn_MouseLeftButtonDown(object sender, MouseButtonEventArgs e) { if (this.person is Student) { Student person = (Student)this.person; person.Rank = (StudentRank)rankComboBox.SelectedItem; } else { Teacher person = (Teacher)this.person; person.Rank = (TeacherRank)rankComboBox.SelectedItem; } this.Close(); } }