Re: can event handler call event source passed as connection point parameter?

"Alexander Nickolov" <>
Tue, 3 Oct 2006 09:31:11 -0700
Now you are jumping to many unfounded conclusions.
I never said anything like that. What I did say is that when
passing a derived interface through a _pure_dispinterface_,
not a COM interface, you get IDispatch* for dual interfaces
and IUnknown* for non-dual interfaces on the other end.
That's all IDispatch::Invoke understands after all, since all
arguments are passed within VARIANTs. A VARIANT can
only contain VT_DISPATCH and VT_UNKNOWN interface
pointers. After marshaling these become IDispatch* and
IUnknown* respectively, with no other methods in the vtables.

Alexander Nickolov
Microsoft MVP [VC], MCSD

"Xudong" <> wrote in message

That means interfaces derived from IDispatch can only be passed as base
Is there a way to change that behavior?
Does this happen within apartment where marshaling is not involved?

Also does this happen on IUnknown?
I saw many SDKs defined COM interfaces as function parameters.

Alexander Nickolov wrote:

IServer is only a convenience in the type library and doesn't
happen in practice. What you get is IDispatch*, which after
marshaling is _only_ IDispatch* - no extra methods in the
vtable. You need to QI to get a full-fledged IServer vtable.

Alexander Nickolov
Microsoft MVP [VC], MCSD

"Xudong" <> wrote in message

Sorry, I simplified what I really had and forgot to write that one. The
actual code did have the correct parameters.
I was really curious why it worked by QueryInterface for its own

Igor Tandetnik wrote:

"Xudong" <> wrote in message

         [id(3)] void OnSomeEvent([in] IServer * ptr, [in] long

So event takes two parameters

    void __stdcall OnSomeEvent(IServer * ptr) {

How come there is only one here?
With best wishes,
    Igor Tandetnik

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