different IDispatch in event handler
 

Hello

I work on a com dll that is called from vba and manipulates a workbook. When
catching the Workbook.SheetActivate event Excel passes the IDispatch
interface of the activated sheet. I then try to compare it to a previously
stored _Worksheet interface after querying it for IDispatch. However this
never succeeds. One thing I cannot understand is that if I first query the
passed IDispatch for the _Worksheet interface everything works as expected.
The IDispatch interface is different from the original one passed to the
event handler.

void EventHandler::OnSheetActivate(IDispatchPtr sheet)
{
// IDispatchPtr does automatic QueryInterface
Excel::_WorksheetPtr ws = sheet; // ws is different from sheet
sheet = ws; // sheet is equal to ws and different from initial value ???

// now compare sheet to stored pointer
// compare succeeds
// if the conversion stuff above is omitted I never find a match for the
stored pointer

// Note: sheet could also be chart, code to handle this case is not
included for brevity
}

Thanks