Microsoft KB Archive/201390

= The CDynamicAccesor class does not handle string columns correctly in Visual C++ =

Article ID: 201390

Article Last Modified on 1/9/2006

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APPLIES TO


 * Microsoft Visual C++ 2005 Express Edition
 * Microsoft Visual C++ .NET 2003 Standard Edition
 * Microsoft Visual C++ .NET 2002 Standard Edition
 * Microsoft Visual C++ 6.0 Enterprise Edition
 * Microsoft Visual C++ 6.0 Professional Edition
 * Microsoft Visual C++ 6.0 Standard Edition

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This article was previously published under Q201390



SYMPTOMS
If you try to update a text column using SetValue function of the CDynamicAccessor class, the column is not updated correctly. 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 the CDynamicAccessor class 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.

