Re: Returning a character buffer from a DLL

Hi All,

 I wrote a simple MFC application and a simple MFC DLL.
 I need to return a string buffer from the DLL in a RunQuery function.

 Please see the code below (Note that I cleared some unrelated lines
like catch, etc, which are not related to my problem now to make code
clearer.)

 If I check the "TheValue.operator _bstr_t().operator char *()" value
in the DLL ,it gives me the correct value!
 But if I check the returned value in the APP, I get junk...

 What is wrong here?

 What I did was as follows (after many trials, and the code shown here
is not necessarily what I think is the correct one...):

-------------------------
 In the App:
-------------------------
char* CSAPI2VPGDlg::GetExtEventID( CString sInternalEventID )
{
    RunQuery(hRC, m_sExtEventID, sInternalEventID); //m_sExtEventID is a
32 bytes char array member

    return m_sExtEventID;
}

-------------------------
 In the DLL:
-------------------------

char* CXDBApp::RunQuery(const CString& a_sQuery)
{
    //Find field
    CString s = a_sQuery;
    CString sField = GetFieldForCollect(s);

    _variant_t TheValue;

    m_pRecordset.CreateInstance(__uuidof(Recordset));
    try
    {
        m_pRecordset->Open((LPCSTR)a_sQuery,
            m_pConnection.GetInterfacePtr(),
            adOpenDynamic,
            adLockOptimistic,
            adCmdText);

        while(!m_pRecordset->adoEOF)
        {
            TheValue = m_pRecordset->GetCollect((char*)_bstr_t(sField));
            if(TheValue.vt!=VT_NULL){
                m_pRecordset->Close();

                //return((char*)_bstr_t(TheValue));
                return TheValue.operator _bstr_t().operator char *();
            }
        }
        m_pRecordset->Close();
    }
}