FIX: RFX_Binary Updates Unchanged CByteArray Data

• The Microsoft Foundation Classes (MFC), included with:
  • Microsoft Visual C++, 32-bit Editions, version 4.2

SYMPTOMS

The MFC ODBC classes attempt to update the CByteArray data for a record each time you move off that record, even if the data was not changed.

If you have a field that cannot be updated, you may receive an error when the update fails. For example, if your recordset contains a SQL Server TIMESTAMP column, you may see the following error:

Can't update a TIMESTAMP column.

CAUSE

The RFX_Binary() function is incorrectly casting the BYTE* data member of the CByteArray to a CByteArray*. Because of this, the CByteArray data always appears to have been changed since the last update.

RESOLUTION

In the DoFieldExchange() of your recordset class, replace calls to RFX_Binary() with calls to the with RFX_Binary_Fix() function.

The following file is available for download from the Microsoft Software Library:

Rfxbinfx.exe

Q119591 How to Obtain Microsoft Support Files from Online Services

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 5.0.

MORE INFORMATION

The RFX_Binary() function is called from within the CRecordset DoFieldExchange() function to handle CByteArray data.

Once you have downloaded Rfxbinfx.exe and run the .exe to extract the RFX_Binary_Fix source code, include RFXBINFX.H in your recordset CPP file.

In your implementation of the DoFieldExchange() function, change each call to RFX_Binary to a call to the RFX_Binary_Fix function.

Additional query words: kbVC420bug kbDSupport IsFieldDirty SetFieldDirty BLOB

Keywords          : kbfile kbDatabase kbMFC kbODBC kbVC kbVC500fix 
Version           : 4.2
Platform          : NT WINDOWS 
Issue type        : kbbug 

Last Reviewed: August 5, 1999