What’s the relationship between MainMenu and MenuStrip?
MenuStrip is a complete replacement for MainMenu and has nothing in common with that control. The old MainMenu was built on top of the built-in Windows support for menus. The GetClientRect() API function automatically deducts the menu size from the client rectangle. MenuStrip doesn’t use Windows menus, thus GetClientRect() returns the size of the window’s client area, disregarding the space taken up by the MenuStrip. The same is true for any other window edge adornments like StatusStrip and ToolStrip, or any docked panels for that matter.
