Yes, the Radio TreeViewItems are grouped per their parent node. But I believe there is a simple and elegant solution for your scenario here - you can use the PreviewChecked event of the RadTreeView and mark all previously checked items unchecked:
sender, RadRoutedEventArgs e)
IList checkedItems =
RadTreeViewItem).CheckState = ToggleState.Off;
Then the item you have checked will be the only one checked in the tree.
You can find this approach realized in the attached sample.
the Telerik team
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