AfxLoadLibrary
Use AfxLoadLibrary to map a DLL module.
HINSTANCE AFXAPI AfxLoadLibrary( LPCTSTR lpszModuleName );
It returns a handle that can be used in GetProcAddress to get the address of a DLL function. AfxLoadLibrary can also be used to map other executable modules.
Each process maintains a reference count for each loaded library module. This reference count is incremented each time AfxLoadLibrary is called and is decremented each time AfxFreeLibrary is called. When the reference count reaches zero, the module is unmapped from the address space of the calling process and the handle is no longer valid.
Be sure to use AfxLoadLibrary and AfxFreeLibrary (instead of the Win32 functions LoadLibrary and FreeLibrary) if your application uses multiple threads and if it dynamically loads an extension DLL. Using AfxLoadLibrary and AfxFreeLibrary insures that the startup and shutdown code that executes when the extension DLL is loaded and unloaded does not corrupt the global MFC state.
Using AfxLoadLibrary in an application requires you to dynamically link to the DLL version of MFC; the header file for AfxLoadLibrary, Afxdll_.h, is only included if MFC is linked to the application as a DLL. This is by design because you have to link to the DLL version of MFC to use or create extension DLLs.
// The following shows how to create a MDI based application // using a generic CView derived class that is implemented in // a dynamically loaded MFC Extension DLL. typedef CRuntimeClass * (*GETDLLVIEW)(); BOOL CUserApp::InitInstance() { // Standard Application Wizard generated initialization excluded. ... // Register the application's document templates. Document templates // serve as the connection between documents, frame windows and views //Load MFC Extension DLL based view class. m_hViewDll = AfxLoadLibrary(szMyViewDllPath); if (!m_hViewDll) { CString str; str.Format(_T("Error: Cannot find component %s"), szMyViewDllPath); AfxMessageBox(str); return FALSE; } GETDLLVIEW GetMyView = (GETDLLVIEW)GetProcAddress(m_hViewDll, "GetMyView"); ASSERT(GetMyView != NULL); CMultiDocTemplate* pDocTemplate; pDocTemplate = new CMultiDocTemplate(IDR_NVC_MFC_DLLUserTYPE, RUNTIME_CLASS(CUserDoc), RUNTIME_CLASS(CChildFrame), // custom MDI child frame GetMyView()); if (!pDocTemplate) return FALSE; AddDocTemplate(pDocTemplate); // Standard Application Wizard generated initalization excluded. ... return TRUE; } int CUserApp::ExitInstance() { if (NULL != m_hViewDll) { AfxFreeLibrary(m_hViewDll); m_hViewDll = NULL; } return CWinApp::ExitInstance(); }
