DOCUMENT:Q152695 04-AUG-2001 [visualc] TITLE :HOWTO: Catch and Decipher DAO SDK-Based Exceptions PRODUCT :Microsoft C Compiler PROD/VER:4.0 4.1 4.2 4.2b 5.0 6.0 OPER/SYS: KEYWORDS:kbcode kbProgramming kbtshoot kbDAOsearch kbDatabase kbMFC kbVC kbVC400 kbVC410 kbVC420 ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - The DAO SDK, included with: - Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1 - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2b - Microsoft Visual C++, 32-bit Professional Edition, version 4.2b - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 - Microsoft Visual C++, 32-bit Professional Edition, version 6.0 - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 ------------------------------------------------------------------------------- SUMMARY ======= This article presents sample code for catching and deciphering exceptions that can be thrown by the DAO SDK class libraries. MORE INFORMATION ================ The following is a sample try/catch loop and helper functions that demonstrate how to decipher either a DAO SDK or MFC-based exceptions. The content of these exceptions is in part (or fully) dumped by using TRACE(). Sample Code ----------- The following code demonstrates a typical try/catch block using C++ Exception Handling for catching the DAO SDK CdbException, or one of the MFC exceptions that the DAO SDK can also throw. CdbDBEngine *pEng = NULL; try { // Call DAO SDK code here pEng = new CdbDBEngine(); //... manipulate dbDao objects here ... } catch( CdbException e ) { AfxDbDaoCatchException( e, pEng ); } catch( CException *e ) { AfxDbDaoCatchException( e ); } catch( ... ) { TRACE( "Caught Win32 Exception\n" ); } if( pEng != NULL ) delete pEng; The implementation of the both over-loaded versions of AfxDbDaoCatchException() follows. You can easily expand the MFC implementation to extract more information from those MFC Exception classes which have additional data members and methods. /////////////////////////////////////////////////////////////////// // // AfxDbDaoCatchException() // // Purpose: Deciphers dbDao (DAO SDK) based exception. // // Parameters: e - Instance of CdbException class. // pEng - Pointer to DBEngine object (via the CdbDBEngine // class). // // Returns: n/a // ////////////////////////////////////////////////////////////////////// void AfxDbDaoCatchException( CdbException &e, CdbDBEngine *pEng ) { // Just in case exception handling code throws an exception try { // It's possible that the engine hasn't been instantiated yet if( pEng == NULL ) { TRACE( _T("Caught CdbException attempting " "to instantiate DBEngine.\n") ); return; } // Log results of exception long nMax = pEng->Errors.GetCount(); TRACE( _T("Caught CdbException, %ld Errors Reported:\n"), nMax ); // Traverse through contents of Errors Collection for( long l = 0; l < pEng->Errors.GetCount(); l++ ) { TRACE( _T("\t #%ld -- %s\n"), pEng->Errors[l].GetNumber(), pEng->Errors[l].GetDescription() ); } // Log results of Last OLE Error. This may or may not be // the same as results stored in the Errors collection. // Ignore CdbLastOLEError.GetHelpFile and // CdbLastOLEError.GetHelpContext CdbLastOLEError exError; TRACE( _T("\t CdbLastOLEError.Source: %s\n"), exError.GetSource() ); TRACE( _T("\t CdbLastOLEError.Description: %s\n"), exError.GetDescription() ); } catch( CException *e2 ) { TRACE( "AfxDbDaoCatchException() " "caught an exception, but was unable to log it\n" ); e2->Delete(); } catch(...) { TRACE( "AfxDbDaoCatchException() " "caught an exception, but was unable to log it\n" ); } } ////////////////////////////////////////////////////////////////////// // // AfxDbDaoCatchException() // // Purpose: Catchs MFC-based exception. // // This code assumes AFXWIN.H and AFXOLE.H have been // included in STDAFX.H // // Parameters: e - Pointer to a class derived from MFC's // CException class. // ////////////////////////////////////////////////////////////////////// void AfxDbDaoCatchException( CException *e ) { // Just in case exception handling code throws an exception try { // Determine name of MFC Exception CString strName; CRuntimeClass *pClass; pClass = e->GetRuntimeClass(); ASSERT( pClass != NULL ); ASSERT( pClass->m_lpszClassName != NULL ); TRACE( _T("Caught MFC Exception of Class: %s\n"), pClass->m_lpszClassName ); // Log additional information about error (if supported) // Only some derived classes from CException support // GetErrorMessage(). if( e->IsKindOf(RUNTIME_CLASS(CFileException) || e->IsKindOf(RUNTIME_CLASS(COleException) || e->IsKindOf(RUNTIME_CLASS(COleDispatchException ) { TCHAR szBuf[256] = _T(""); UINT nHelpContextId; BOOL bRetVal = TRUE; e->GetErrorMessage( szBuf, 256, &nHelpContextId ); if( strlen( szBuf ) > 0 ) { TRACE( _T("\t Error Message = %s\n"), szBuf ); } } } catch( CException *e2 ) { TRACE( "AfxDbDaoCatchException() " "caught an exception, but was unable to log it\n" ); e2->Delete(); } catch(...) { TRACE( "AfxDbDaoCatchException() " "caught an exception, but was unable to log it\n" ); } // Step 3: Delete Exception e->Delete(); } Additional query words: ====================================================================== Keywords : kbcode kbProgramming kbtshoot kbDAOsearch kbDatabase kbMFC kbVC kbVC400 kbVC410 kbVC420 kbVC500 kbVC600 Technology : kbAudDeveloper kbDAOsearch kbSDKDAOSearch kbSDKSearch Version : 4.0 4.1 4.2 4.2b 5.0 6.0 Issue type : kbhowto ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. 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