Same answer as before... When you used the class wizard to put a string in, where did you put it.
And to reflect your question back at you... Where else can member variables be if not part of an object.
The DDX_xxxx functions will work on any int / CString / thing, but unless you have a good reason to work on something that's not a member of the dialog class that the DoDataExchange method is a member of, don't do it!
As your understanding is obviously basic [*], I'd stay with boring defualt stuff for now.
[*] No offense: We all were beginners once. I'll only insult people if they fail to learn, not when they're starting.
In the process of moving to Sweden for love (awwww).
If you're in Scandinavia and want an MVP on the payroll (or happy with a remote worker), give me a job!