As I managed to understand you want to have CheckBoxes on all of your RadTreeViewItems and some of them should be disabled (for particular items). Since your RadTreeView is bound , you have to create a Custom Style of the RadTreeViewItem (edit the default one and set IsReadOnly to true on the CheckBox element) and the use StyleSelector to set this custom style only to particular items. You may find these article helpful:
Styling the RadTreeViewItem
Please let us know if you need further assistance or info.
the Telerik team
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