DOCUMENT:Q201390 07-MAY-2001 [visualc] TITLE :PRB: CDynamicAccesor Does Not Handle String Columns Correctly PRODUCT :Microsoft C Compiler PROD/VER:winnt:6.0 OPER/SYS: KEYWORDS:kbATL kbDatabase kbProvider kbVC600 kbGrpDSVCDB ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 - Microsoft Visual C++, 32-bit Professional Edition, version 6.0 - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 ------------------------------------------------------------------------------- SYMPTOMS ======== If you try to update a text column using SetValue function of class CDynamicAccessor, the column is not updated properly. Furthermore, the debug version of your OLE DB client program may ASSERT on the following line in ATLDBCLI.H: ATLASSERT(m_pColumnInfo[nColumn].ulColumnSize == sizeof(ctype)); CAUSE ===== The SetValue function of CDynamicAccessor is a templated function to set the value of columns of most data types. This function does not handle strings correctly. Following is sample code that tries to update a text column using the SetValue function: void UpdateCol() { HRESULT hr; char szColVal[] = "Newval"; CDataSource ds; CSession ses; hr = ds.Open("MSDASQL","Ram","sa",""); hr = ses.Open(ds); CDBPropSet propset(DBPROPSET_ROWSET); propset.AddProperty(DBPROP_IRowsetChange, true); propset.AddProperty(DBPROP_UPDATABILITY, DBPROPVAL_UP_CHANGE | DBPROPVAL_UP_INSERT | DBPROPVAL_UP_DELETE); CTable< CDynamicAccessor > tb; // Open a rowset on a table with Dynamic accessor hr = tb.Open(ses,"Authors",&propset); tb.MoveFirst(); tb.SetValue((ULONG)1L,(char *)szColVal); // Call this function to set the data hr = tb.SetData(); } This code does not update the column with the given value. RESOLUTION ========== To avoid this problem with text columns, copy the following string directly to the column's buffer: void CMultipleDlg::OnUpdate() { HRESULT hr; char szColVal[] = "Newval"; CDataSource ds; CSession ses; hr = ds.Open("MSDASQL","Ram","sa",""); hr = ses.Open(ds); CDBPropSet propset(DBPROPSET_ROWSET); propset.AddProperty(DBPROP_IRowsetChange, true); propset.AddProperty(DBPROP_UPDATABILITY, DBPROPVAL_UP_CHANGE | DBPROPVAL_UP_INSERT | DBPROPVAL_UP_DELETE); CTable tb; // Open a rowset on a table with Dynamic accessor hr = tb.Open(ses,"Authors",&propset); tb.MoveFirst(); void *pName; // Get the address of the buffer for the second column pName = tb._GetDataPtr(1L); // copy the string to be set to the buffer strcpy((char *)pName,szColVal); // Call this function to set the data hr = tb.SetData(); } STATUS ====== This behavior is by design. REFERENCES ========== OLE DB template classes documentation on MSDN Additional query words: kbDSupport ====================================================================== Keywords : kbATL kbDatabase kbProvider kbVC600 kbGrpDSVCDB Technology : kbVCsearch kbAudDeveloper kbVC600 kbVC32bitSearch Version : winnt:6.0 Issue type : kbprb ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2001.