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

• The Microsoft Foundation Classes (MFC), included with:
  • Microsoft Visual C++, 32-bit Editions, versions 4.2, 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
Version : 4.2 4.2b
Platform : NT WINDOWS
Issue type : kbbug