Q125727: FIX: Text Truncated When Using Dynaset and RFX_Text()

Article: Q125727
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): kbDatabase kbMFC kbODBC kbVCkbbuglist kbfixlist
Last Modified: 23-JUL-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), included with:
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, version 2.0 
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SYMPTOMS
========

When editing a record with a text field, the text gets truncated to the length
of the previous value. For example, if a text field has the value "ABC" and an
application attempts to change the value to "TEST," the result is "TES."

This occurs when opening a CRecordset with CRecordset::dynaset as the first
argument of CRecordset::Open() and using RFX_Text() to map the field to a
CRecordset member variable.

CAUSE
=====

The CFieldExchange::Default() function, located in \MSVC20\MFC\SRC\DBRFX.CPP,
contains the following code:

  case BindFieldForUpdate:
     if (!m_prs->IsFieldFlagDirty(nField, m_nFieldType))
     {
       // If field is not dirty, set bound length to SQL_IGNORE
       // for SQLSetPos updates
       *plLength = SQL_IGNORE;
     }
     else if ((m_prs->m_nEditMode == CRecordset::addnew) &&
             (!m_prs->IsFieldFlagNull(nField, m_nFieldType)))
     {
       // plLength always set to SQL_NULL_DATA in AddNew mode
       *plLength = cbValue;
     }
     return;

The second If statement shouldn't check for only CRecordset::addnew because this
also applies to updates.

RESOLUTION
==========

To work around this problem, perform these steps:

1. In one of your header files, perhaps in your CRecordset's header file, create
  the following function prototype:

      void RFX_Text2(CFieldExchange* pFX, const char *szName,
         CString& value, int nMaxLength=255, int nColumnType=SQL_VARCHAR);

2. In your CRecordset's .CPP file or elsewhere, add the RFX_Text2() definition
  shown below:

     ****
     void RFX_Text2(CFieldExchange* pFX, const char *szName,
                    CString& value, int nMaxLength, int nColumnType)
     {
       ASSERT(AfxIsValidAddress(pFX, sizeof(CFieldExchange)));
       ASSERT(AfxIsValidString(szName));
       ASSERT(AfxIsValidAddress(&value, sizeof(CString)));

       if (pFX->m_nOperation==CFieldExchange::BindFieldForUpdate)
       {
         UINT nField;
         if (!pFX->IsFieldType(&nField))
           return;

      LONG* plLength = pFX->m_prs->GetFieldLength(pFX);

      if (!pFX->m_prs->IsFieldFlagDirty(nField, pFX->m_nFieldType))
      {
        // If field is not dirty, set bound length to SQL_IGNORE
        // for SQLSetPos updates
        *plLength = SQL_IGNORE;
      }
      else if (!pFX->m_prs->IsFieldFlagNull(nField, pFX->m_nFieldType))
      {
        // plLength always set to SQL_NULL_DATA in AddNew mode
        *plLength = value.GetLength();
      }
      return;
       }

       RFX_Text(pFX, szName,value, nMaxLength,nColumnType);
     }

     ****

3. Modify the DoFieldExchange member function of your CRecordset class,
  replacing calls to RFX_Text with calls to the RFX_Text2 function described
  above.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug was corrected in Visual C++ version 2.1.

Additional query words: 2.00 3.00

======================================================================
Keywords          : kbDatabase kbMFC kbODBC kbVC kbbuglist kbfixlist
Technology        : kbAudDeveloper kbMFC
Version           : winnt:
Issue type        : kbbug
Solution Type     : kbfix

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

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