>I copied the program to the Window 10 tablet via USB (no problems with WD). Now your program correctly responds to me turning the tablet to portrate or landscape. That is, the word "Portrate" changes to "Landscape" on the form, and back. Is this what you were trying to confirm?

Yes, that, and changing between tablet and desktop modes, and recognizing that is running in a tablet (of course, this last one won't change during the execution of the program, so it is just a state that is read once, and displayed at the form's title).

Thank you very much, Dmitry. You're confirming my first findings, but, on the other hand, you have a setup close to mine, I think. Hopefully, I'll gather other more heterogeneous inputs (here or at other forums), and extend the class one piece at a time.