Passing interface derived from IDispatch as a parameter

"Igor R." <>
Mon, 4 Jan 2010 05:28:33 -0800 (PST)

Is it possible to get a dual interface (not IDispatch!), passed as a
parameter to Invoke, marshaled correctly?

I've got a source dispinterface with a method defined like this:
[id(1), helpstring("method notify")] HRESULT notify([in] IMySender

where IMySender is:

interface IMySender : IDispatch

So in the CP implementation I've got a code like this:

HRESULT Fire_Notify(int id, IMySender *sender)
  //iterate through connections...
  CComVariant avarParams[1];
  avarParams[0] = sender;
  avarParams[0].vt = VT_DISPATCH;
  CComVariant varResult;
  DISPPARAMS params = { avarParams, NULL, 1, 0 };
  hr = pConnection->Invoke(id, IID_NULL, LOCALE_USER_DEFAULT,
DISPATCH_METHOD, &params, &varResult, NULL, NULL);

However, this doesn't work when the event is fired into another
apartment: IMySender is not marshaled well (only IDispatch part of it
is actually marshaled), so that any call to its methods crashes.
"Dirty" workaround is to perform explicit QI:

void onNotify(IMySender *sender)
  IDispatch *disp = sender;
  CComQIPtr<IMySender> goodSender(disp);

My question is whether it's possible to pass "typed" interface
correctly in such situation?

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