C / C++ / MFC

CStatic* pCStatic = (CStatic*) GetDlgItem(IDC_STATIC1);
HWND hWnd = pCStatic->m_hWnd;

UINT_PTR CALLBACK MyOFNHookProc( HWND hdlg,  // handle to child dialog box
        UINT uiMsg,  // message identifier
        WPARAM wParam, // message parameter
        LPARAM lParam // message parameter
        )
{
 int nResult = FALSE;
 
 if (hdlg == NULL) 
  return 0;
#ifdef _DEBUG
 // from "_AfxCommDlgProc()" of the file "dlgcomm.cpp"
 _AFX_THREAD_STATE* pThreadState = AfxGetThreadState();
 // =_AfxActivationWndProc(hwnd,uint,uint,long)
 if (pThreadState->m_pAlternateWndInit != NULL) 
  pThreadState->m_pAlternateWndInit = NULL;
#endif
 

 switch(uiMsg)
 {
 
 case WM_NOTIFY:
  {
   LPOFNOTIFY pOfn = (LPOFNOTIFY)lParam;
   switch(pOfn->hdr.code)
   {
   case CDN_SELCHANGE:
    {
     TCHAR dummy_buffer;
 
     // Get the required size for the 'files' buffer
     HWND hOwner = GetParent(hdlg);
     HWND hParent = GetParent(hOwner);
     UINT nfiles = CommDlg_OpenSave_GetSpec(hOwner, &dummy_buffer, 1);
 
     // Get the required size for the 'folder' buffer
     int cbLength = CommDlg_OpenSave_GetSpec(GetParent(hdlg), NULL, 0);
 
     cbLength += _MAX_PATH;
 
     if(cbLength>(pOfn->lpOFN)->nMaxFile)
     {
 
      if((pOfn->lpOFN)->lpstrFile)
       HeapFree(GetProcessHeap(),
       0,
       (pOfn->lpOFN)->lpstrFile);
 
      (pOfn->lpOFN)->lpstrFile = (LPTSTR) HeapAlloc(GetProcessHeap(),
       HEAP_ZERO_MEMORY,
       cbLength);
            (pOfn->lpOFN)->nMaxFile = cbLength;
     }
 
     nResult = TRUE;
     break;
    }
   default:
    break;
   }
   break;
  }
 default:
  break;
 }
 return nResult;
}
 
// call function
void CMultiSelectDlg::OnButton1() 
{
  #define NAMEBUF 1024
 
 TCHAR szFilters[]= _T("MyType Files (*.doc)|*.doc||");
 
   CFileDialog fileDlg(TRUE, _T("doc"), _T("*.doc"),
  OFN_FILEMUSTEXIST | OFN_HIDEREADONLY|OFN_ALLOWMULTISELECT, szFilters);
 
   fileDlg.m_ofn.lpstrFile= (LPTSTR) HeapAlloc(GetProcessHeap(),
  HEAP_ZERO_MEMORY,
  NAMEBUF);
 
 fileDlg.m_ofn.nMaxFile = NAMEBUF;   // redefine nMaxFile 
 fileDlg.m_ofn.lpfnHook = (LPOFNHOOKPROC)MyOFNHookProc;
  
 INT_PTR ret = fileDlg.DoModal();
 if (ret == IDOK)
 {
  int width = 0;
  CString str;
  CDC *pDC = m_listbox.GetDC();
  int saved = pDC->SaveDC();
  pDC->SelectObject(GetFont());
 
  UINT count = 0;
 
  POSITION pos = fileDlg.GetStartPosition();
  while (pos)
  {
   str = fileDlg.GetNextPathName(pos);
   m_listbox.AddString(str);
   CSize size(0, 0);
   size = pDC->GetTextExtent(str);
   width = width > size.cx ? width : size.cx;
   ++count;
  }
  pDC->RestoreDC(saved);
  ReleaseDC(pDC);
  m_listbox.SetHorizontalExtent(width + 5);
 
  str.Format(_T("%u files selected"), count);
  m_static.SetWindowText(str);
 }
 DWORD dwCode = CommDlgExtendedError();
 if (FNERR_BUFFERTOOSMALL==dwCode)
 {
  int i =0;
 }
 
 HeapFree(GetProcessHeap(),0,
  (fileDlg.m_ofn.lpstrFile));
}