CWnd* CWinThread::GetMainWnd()
{
    if (m_pActiveWnd != NULL)
        return m_pActiveWnd;    // probably in-place active

    // when not inplace active, just return main window
    if (m_pMainWnd != NULL)
        return m_pMainWnd;

    return CWnd::GetActiveWindow();
}

If your application is an OLE server, call this function to retrieve a pointer to the active main window of the application instead of directly referring to the m_pMainWnd member of the application object.