PRB: When to Call AfxDaoTerm() in an Automation Server

RESOLUTION

MFC keeps an internal object lock count of automation objects in the module state. The constructor of each object exposed by the automation server calls AfxOleLockApp() to increment this count and calls AfxOleUnlockApp() to decrement it.

An MFC DLL automation server gets unloaded when the AfxOleCanExitApp() function returns TRUE. This function checks the object lock count and returns TRUE if no objects are in use. The default implementation of DllCanUnloadNow() in an AppWizard-generated automation server looks like this:

   STDAPI DllCanUnloadNow(void)
   {
       AFX_MANAGE_STATE(AfxGetStaticModuleState());
       return AfxDllCanUnloadNow();
   }
				

Add the following code to terminate DAO when no automation objects are in use any longer:

   STDAPI DllCanUnloadNow(void)
   {
       AFX_MANAGE_STATE(AfxGetStaticModuleState());

       if (AfxOleCanExitApp())
           AfxDaoTerm();

       return AfxDllCanUnloadNow();
   }