private void VorfuehrungCollection_ItemRemoved(object sender, Tortuga.Anchor.ComponentModel.ItemEventArgs <Vorfuehrung> e)
 {
     ModelChanged?.Invoke(this, new EventArgs());
 }
 private void BuchungCollection_ItemAdded(object sender, Tortuga.Anchor.ComponentModel.ItemEventArgs <Buchung> e)
 {
     ModelChanged?.Invoke(this, new EventArgs());
 }