This silverlight tree view does not have a loadondemand method, right?
I have try to use this funtionality using the itemexpansionchanging event
and add the sub items
if (e.IsExpanded)
e.SourceItem.Items.Add(new Node)
but I am having problems with this...
Keep an eye on our 10.3 release, which is slated for the next couple of weeks. We have a virtualized tree that should achieve what you need.