DocumentModelTreeViewer is a custom class that we use only in the demos - you can view its source code
in the samples solution installed with the controls - basically it presents document structure as a tree.
If you want to create full featured editing UI, you can look at our blog post
describing how to do that using the Visual Studio designer - it is not nessesary to reference MSWordExample user control.
Don't hesitate to contact us if you have other questions.
the Telerik team
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