FIX: Date/Time Fields Fail to Update When Using a Dynaset

The information in this article applies to:

• The Microsoft Foundation Classes (MFC), included with: Microsoft Visual C++, 32-bit Edition, version 2.0

SYMPTOMS

An attempt to update a date/time field using a CTime object will fail. The CRecordset::RFX_Date() doesn't work correctly, and the date/time field in the database table isn't changed. This problem occurs only when passing CRecordset::dynaset as the first parameter to the CRecordset::Open() member function.

CAUSE

The RFX_Date() function that takes a CTime object as a parameter fails to transfer the CTime data to its TIMESTAMP_STRUCT proxy before performing an update.

RESOLUTION

To work around this problem, follow these steps:

1. In one of the header files, such as the CRecordset's header file, create the following function prototype:

      void RFX_Date2( CFieldExchange* pFX, const char* szName, CTime& value );
   
   

2. In the CRecordset's .CPP file or elsewhere, add this RFX_Date2() definition:

      void RFX_Date2(CFieldExchange* pFX, const char *szName,
         CTime& value)
      {
       ASSERT(AfxIsValidAddress(pFX, sizeof(CFieldExchange)));
   
       if (pFX->m_nOperation==CFieldExchange::BindFieldForUpdate)
       {
               if(pFX->m_nFieldType == CFieldExchange::param)
                   return;
   
               //pFX-m_nFields hasn't been incremented yet so no need to
               // subtract 1 for indexing m_pvFieldProxy
               if (pFX->m_prs->m_pvFieldProxy[pFX->m_nFields] != NULL)
               {
                   // Fill buffer (expected by SQLSetPos) with new field data
                   TIMESTAMP_STRUCT* pts;
                   pts = (TIMESTAMP_STRUCT*)
                      pFX->m_prs->m_pvFieldProxy[pFX->m_nFields];
                   pts->year = (SWORD)value.GetYear();
                   pts->month = (UWORD)value.GetMonth();
                   pts->day = (UWORD)value.GetDay();
                   pts->hour = (UWORD)value.GetHour();
                   pts->minute = (UWORD)value.GetMinute();
                   pts->second = (UWORD)value.GetSecond();
                   pts->fraction = 0;
               }
          }
          RFX_Date(pFX, szName, value);
      }
   
   

3. Modify the DoFieldExchange member function of the CRecordset class, replacing calls to RFX_Date with calls to the RFX_Date2 function described above.

STATUS

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

MORE INFORMATION

MFC Technote #43 contains more information about record field exchange (RFX) functions and CFieldExchange operations.