FIX: Text Truncated When Using Dynaset and RFX_Text()

The information in this article applies to:

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

      - Microsoft Visual C++, 32-bit Edition, version 2.0
  

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;

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.