When you start to make the interface, all the defined variables are fine, and the interface is still usable!
But after adding a program under one of the "buttons", it says that the variables above are "undeclared identifier",
Excuse me, why?
It is of type "CString"!
The above variable is not used in the added program, and it is not involved at all. It is unclear why the prompt prompts that the variable is wrong?