Microsoft KB Archive/172391

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SAMPLE: GetRows.exe Demonstrates #import with ADO and GetRows()

Last reviewed: July 13, 1998
Article ID: Q172391



The information in this article applies to: ActiveX Data Objects (ADO) included with:

    - Microsoft Visual C++, 32-bit Editions, version 5.0

SUMMARY

GetRows.exe is a sample that is identical to the ADO GetRows sample that comes with the OLEDBSDK, but GetRows.exe is re-written to use the #import compiler directive, which was introduced in Visual C++ version 5.0. The code is much cleaner using #import and is less error-prone.

MORE INFORMATION

The following file is available for download from the Microsoft Software Library:

 ~ GetRows.exe (size: 599958 bytes) 

For more information about downloading files from the Microsoft Software Library, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q119591
   TITLE     : How to Obtain Microsoft Support Files from Online Services

The demonstration code resides in two primary functions; OnExecute and DoGetRows(). Here is the code:

   #import "c:\program files\Common Files\System\ADO\MSADO10.DLL" \
      implementation_only

   const _bstr_t bstrSource(_T("DRIVER=Microsoft Access Driver"
      "(*.mdb);DBQ=nwind.mdb"));
   const _bstr_t bstrUser(_T("Admin"));
   const _bstr_t bstrPassword(_T(""));
   const _bstr_t bstrSQL(_T("select EmployeeId, LastName, FirstName from"
      "Employees"));

   void CVC5GetRowsDlg::OnExecute()
   {
      HRESULT hr;
      try
      {

         if ( m_pConn == NULL || m_pRS == NULL)
         {
            hr = CoInitialize(NULL);
            if (FAILED(hr))
            {
               AfxMessageBox(_T("Failure to Initialize OLE"));
               return;
            }

            m_pConn.CreateInstance(_uuidof(ADODB::Connection));

            m_pConn->Open( bstrSource, bstrUser, bstrPassword );

            m_pRS.CreateInstance(_uuidof(ADODB::Recordset));

            m_pRS->PutSource(bstrSQL);

            m_pRS->ActiveConnection = m_pConn;

            _variant_t vNull;
            vNull.vt = VT_ERROR;
            vNull.scode = DISP_E_PARAMNOTFOUND;

            m_pRS->Open(vNull, vNull, ADODB::adOpenKeyset,
                        ADODB::adLockOptimistic,  ADODB::adCmdUnknown);
        }

        // Perform the two GetRows functions
        DoGetRows();

        // Reset the recordset
        m_pRS->MoveFirst();

      }
      catch(_com_error & err)
      {
     ::MessageBox(NULL, (LPCSTR)err.Description(), _T("ADO Error"), MB_OK);
      }
   }

   void CVC5GetRowsDlg::DoGetRows()
   {
      ASSERT(m_pRS!=NULL);

      HRESULT hr;
      _variant_t cRows;
      _variant_t varField, varNewField;
      CString strLBRow;
      LONG lNumOfCol, lNumRecords;
      LONG   lIndex[2];
      CListBox *pListBox = (CListBox *)GetDlgItem(IDD_GETROWSLIST);

      //Perform GetRows on Employee table

      // NOTE: #import generates vtMissing for default arguments which
      //       evaluates to a variant with vt=VT_ERROR and
      //       scode = DISP_E_PARAMNOTFOUND.
      //       vtMissing is used for the optional second and third
      //       arguments in the GetRows call.  If vtMissing is used,
      //       GetRows starts from the current record and gets all columns
      cRows = m_pRS->GetRows(ADODB::adGetRowsRest);

      //Find out how many records were actually retrieved
      //(SafeArrays are 1-based)
      lNumOfCol = 2;
      SafeArrayGetUBound(cRows.parray, 2, &lNumRecords);

      //Clear the listbox
      pListBox->ResetContent();

      for (lIndex[1] = 0; lIndex[1] <= lNumRecords; lIndex[1]++)
      {
         strLBRow.Empty();//Clear the string

         for (lIndex[0] = 0; lIndex[0] <= lNumOfCol; lIndex[0]++)
             // get 3 columns
         {
            SafeArrayGetElement(cRows.parray, &lIndex[0], &varField);

            hr = VariantChangeType(&varNewField, &varField, 0, VT_BSTR);

            if(hr == S_OK)
            {
               strLBRow += (LPCWSTR)varNewField.bstrVal;
               if (lIndex[0] != lNumOfCol)
               strLBRow += _T(", ");
            }
            varField.Clear();
            varNewField.Clear();
         }
      pListBox->AddString(strLBRow);
      }
   }

For additional information, please see the following articles in the Microsoft Knowledge Base:

   ARTICLE-ID: Q169496
   TITLE     : INFO: Using ActiveX Data Objects (ADO) via #import in VC++

   ARTICLE-ID: Q166112
   TITLE     : PRB: Conflict with EOF When Using #import with ADO

   ARTICLE-ID: Q169498
   TITLE     : INFO: Extracting Error Information from ADO in VC++ with
               #import

   ARTICLE-ID: Q172394
   TITLE     : FILE: ADOReg.exe License Key Registration DLL and ADO Use
               Tips



Additional query words:

Keywords : kbcode kbfile kbsample adovc
Technology : odbc
Version : WINDOWS:
Platform : WINDOWS


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Last reviewed: July 13, 1998
© 1998 Microsoft Corporation. All rights reserved. Terms of Use.