Hi David Cardona,
The LoadOnDemand can work in your scenario.
When you set the IsLoadOnDemandEnabled on the TreeView it gets inherited for all TreeViewItems.
If you know that an item will not have children, you can sets its IsLoadOnDemandEnabled property to false (this can happen in the ItemPrepared event of the TreeView for example).
Then you just need to handle the LoadOnDemand event which supplies you with the item that is being expanded. You can start an async retrieval and populate the item's children when you have the result.
More information is available here:
I am also attaching a sample project that demonstrates this with LoadOnDemand.
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