I was writing a piece of code to store and load user preferences and wanted to persist the properties of some ActiveX controls on my dialog. The following procedure seems to do the job rather nicely.
This can then be called simply by doing the following:
BOOL PersistActiveX(CArchive& ar, CWnd* pActiveX)
HRESULT hr = E_FAIL;
// Create an archive stream
LPPERSISTSTREAMINIT pPersStm = NULL;
LPUNKNOWN lpUnk = pActiveX->GetControlUnknown();
// We have the IUnknown interface, so
// get the IPersistStreamInit
// We have the relevant interface so load or save the data
// based on the type of archive we have.
hr = pPersStm->Load(&stm);
hr = pPersStm->Save(&stm, FALSE);
// Must release the interface