public override void Dispose()
{
base.Dispose();
RelatedNodeListBoxViewModel.ItemSelected -= OnRelatedNodeSelected;
RelatedNodeListBoxViewModel.Items.CollectionChanged -= OnRelatedNodeCollectionChanged;
RelatedNodeListBoxViewModel.Dispose();
DiagramEventSource.DiagramChanged -= OnDiagramChanged;
UnsubscribeFromViewportEvents();
DiagramViewportViewModel.Dispose();
}