My goal is to be able to capture what's behind the form, which works on win7, win8, win10, if it's very difficult I can pay to do it for myself.
Yeah I understood that, but WHY do you want to do that?
I need to do this, to monitor what's behind the form
My program will work this way, visible to the client all time, I can see what is behind the form
Mhh sorry, I guess I cant help you with that. Not sure whats the purpose of such a program. You could use
PrintWindow for specific windows (you might even be able to compose your own "desktop" by iterating through all visible windows). This should work for background windows, but might not work for minimized ones.