The CDynamicAccesor class does not handle string columns correctly in Visual C++ (201390)
The information in this article applies to:
- Microsoft Visual C++ 2005 Express Edition
- Microsoft Visual C++ .NET (2003)
- Microsoft Visual C++ .NET (2002)
- Microsoft Visual C++, 32-bit Enterprise Edition 6.0
- Microsoft Visual C++, 32-bit Professional Edition 6.0
- Microsoft Visual C++, 32-bit Learning Edition 6.0
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<CDynamicAccessor> 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
| Modification Type: | Major | Last Reviewed: | 1/9/2006 |
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| Keywords: | kbtshoot kbDatabase kbprb kbProvider KB201390 kbAudDeveloper |
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