Is it possible to pass (copy and paste, or something similar) controls from a web project to a desktop project and viceversa?
It does not work directly. BUT you can copy/paste events and methods. Lets say you have a desktop app and want to port it to web, you must recreate the interface, but afterwards, copy the action for buttons, and methods to the web pages. If your code is clean, it should work pretty rapidly 
Thank you. It´s a pitty but I´ll try.
FWIW, we are working towards being able to do exactly what you want.: copy and paste controls between different project types.