Indeed, you are absolutely right, the help article seems to be outdated. Please excuse us for the inconvenience caused. I have updated your Telerik points accordingly.
However, you can find this example in our online demo
. You can find the same example in your local copy of WPF demos.
We will do our best to provide a working example that meets your requirements. We will post it here as soon as it is ready.
All the best,
the Telerik team