Introduction - If you have any usage issues, please Google them yourself
First, keep the menu resource ID is IDR_MAINFRAME. MDI child window to delete the menu along with a menu resource with the ID (IDR_xxxTYPE) the type of reasons for doing so is to avoid resource leaks, (where the leak, I did not go check, MSDN is this description), the MDI window , open the child window when the menu switching will occur, these are the MFC code automatically, so we are now is to switch the menu code to remove them.