How to read Unicode data in Oracle?

Hi,

Does anyone know how to read Unicode data in Oracle database and write onto a text file? Because when I read it, some Unicode charaters change to "¿".

My code is:

void CMyDlg::ReadUnicode()
{
   _RecordsetPtr recordset = NULL;
   _CommandPtr command = NULL;
    _variant_t vRowsAffected;
    _variant_t vNull;
    vNull.vt = VT_ERROR;
    vNull.scode = DISP_E_PARAMNOTFOUND;
    HRESULT hr;
    hr = recordset.CreateInstance(__uuidof(Recordset));
    hr = command.CreateInstance(__uuidof(Command));

    command->ActiveConnection = GetConnection();
    command->CommandType      = adCmdText;
    command->CommandText      = "SELECT TEXT FROM UNICODE WHERE ID=1";

    recordset = command->Execute(&vRowsAffected, &vNull, adCmdText);

    if (recordset!=NULL)
    {
      recordset->MoveFirst();
      while (!recordset->adoEOF)
      {
             _variant_t vcode = recordset->Fields->GetItem(L"TEXT")->GetValue();
          recordset->MoveNext();
      }
    }
    recordset->Close();
    command->Release();
}

I have a string "đăng" stored in Oracle database and it displays in memory when I view it: "00142BBC  BF 00 BF 00 6E 00 67  ¿.¿.n.g".

Please help,
Thanks