title: MFC: Resource added, but there's still an undeclared identifier for the resource id
body: <p>I'm trying to add a popup menu to a project, let's call it ProjectA. In VS2010, I would right click ProjectA from the Resource View, and click Add>Resource from the context menu. </p>
  
  <p>Then I would double click the Menu icon, and edit the resource to my wishes. Upon editing this menu, I noticed that I could not edit the ID or file name of the resource. The default name was "IDR_MENU2". </p>
  
  <p>However, I was able to edit the menu items' IDs, such as ID_MENU_COPY and ID_MENU_PASTE.</p>
  
  <p>When I tried to use it in one of the files of ProjectA, I would get an error, "Undeclared identifier", for those IDs. </p>
  
  <p>I even tried to add some resources to the String Table of ProjectA, and those IDs were still invalid when used in the program.</p>
  
  <p>Why is that happening? I'm also quite new to MFC (super beginner).</p>