FIX: Text Truncated When Using Dynaset and RFX

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:

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);

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);

   }

   ****

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

FIX: Text Truncated When Using Dynaset and RFX_Text() (125727)

SYMPTOMS

CAUSE

RESOLUTION

STATUS