Thank you for your question.
Actually, the Telnet class is not a real class and its purpose was just to fit in a scenario involving a long-running process. Since many users were confused, because of this class, we removed the article from our Knowledge Base section and now you are only able to access the article if you have a direct link to it. Generally, the RadWaitingBar API is covered by our Step-by-step Tutorial for WinForms
For your convenience, however, I am attaching a sample project which follows the approach of the Knowledge Base article substituting the Telnet scenario with another time-consuming operation.
I hope this helps.
All the best,
the Telerik team
Q1’11 SP1 of RadControls for WinForms is available for download
; also available is the Q2'11 Roadmap
for Telerik Windows Forms controls.