I have a similar requirement but in my case I need the expander to look like it has items underneath it (arrow facing down for example).
I did something similar to this on a TreeListView by setting the "IsExpandable" property to true during the RowLoaded event. Is there something similar on the TreeView?
You can follow the same approach but define a custom style for the Expander element of the RadTreeViewItems. The RadTreeView control exposes a ExpanderStyle property that allow you to set a custom style for the expander element of the items.
Please take a look at the sample I attached and let me know if it helps.
Greetings,
Tina Stancheva
the Telerik team
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