void kundenSuchenControl_KundeGefunden(object sender, KundeEventArgs e) {
     this.listBoxKunden.SelectedItem = e.Kunde;
 }
 void kundenDetailsControl_ChangeKunde(object sender, KundeEventArgs e) {
     //Object o = listBoxKunden.SelectedItem;
     updateListBoxKunden();
     listBoxKunden.SelectedItem = e.Kunde;
 }