Q159956: FIX: Dirty Flag Not Cleared During Edit() or Update()

Article: Q159956
Product(s): Microsoft C Compiler
Version(s): 4.2 4.2b
Operating System(s): 
Keyword(s): kbDatabase kbMFC kbODBC kbVC kbVC500fix
Last Modified: 04-AUG-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Microsoft Foundation Classes (MFC), included with:
   - 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 
-------------------------------------------------------------------------------

SYMPTOMS
========

When you use the Microsoft Foundation Classes (MFC) ODBC to update a record that
has not been modified since the last call to CRecordset::Update(), the fields
within the record show up as dirty.

CAUSE
=====

Neither the CRecordset::Edit() function nor the CRecordset::Update() function
clear the dirty flag.

RESOLUTION
==========

Override CRecordset::Update() and clear the dirty flags for your recordset after
calling the base class CRecordset::Update().

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug has been fixed in Visual C++ version 5.0.

MORE INFORMATION
================

The following sample code displays the problem. The second sample shows how to
implement the workaround:

Sample Code 1
-------------

     // m_pSet is a pointer to a CRecordset derived class, called CMySet,
     // that has a text member variable called m_Name.

     m_pSet->Edit();
     m_pSet->m_Name = "NewName";
     m_pSet->Update();

     m_pSet->Edit();
     if( m_pSet->IsFieldDirty( &(m_pSet->m_Name) ) )
         TRACE( "Name is dirty\n" );
     // The next call will update the record, even though the data has
     // not changed.
     m_pSet->Update();

Sample Code 2
-------------

     // Override CRecordset::Update and clear the dirty flags:
     BOOL CMySet::Update()
     {
        BOOL bReturn = CRecordset::Update();
        if (m_bCheckCacheForDirtyFields &&
           !(m_dwOptions & optimizeBulkAdd))
        {
           SetFieldDirty(NULL, FALSE);
        }
        return bReturn;
     }

Additional query words: kbVC420bug kbDSupport

======================================================================
Keywords          : kbDatabase kbMFC kbODBC kbVC kbVC500fix 
Technology        : kbAudDeveloper kbMFC
Version           : 4.2 4.2b
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.