CreateObject failed with VB.Net, but succeded with VB6

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Dmitry Zhiltsov - 15 Sep 2003 07:49 GMT

There some problems with creating object our COM server
application. Application works fine, if we use VB6 ( or
any old tool supported automation ) for creating client
application, but the same code failed in vb.net with very
strange error message: your COM server does not support
IDispatch or ( IMyApp ), depending on object requested (
dim a as Object or dim a as MyApp ). Have somebody any
idea of such vb.net behaviour?

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Phil Wilson - 16 Sep 2003 18:20 GMT

VB6 isn't an "automation only" interface - it will early-bind and use vtables
depending on how your code accesses the COM object, so it may well be true that
you don't have IDispatch.

I sssume you're exposing a .NET class as a COM interface, so post the heading
and attributes for your .NET class, and the Interface too if you're using one.

Signature

Phil Wilson [MVP Windows Installer]
----

> There some problems with creating object our COM server
> application. Application works fine, if we use VB6 ( or
[quoted text clipped - 4 lines]
> dim a as Object or dim a as MyApp ). Have somebody any
> idea of such vb.net behaviour?

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Dmitry Zhiltsov - 17 Sep 2003 10:16 GMT

Thanks for help. I found the difference VB.Net object creation sequence
from vb6 one and correct mistake in our server code. VB6 hold reference
on class factory much longer then VB.Net( VB.Net release class factory
immediatly after use ). We had not 0 reference count on our object in
some moment after CreateInstance call, but VB.6 worked fine, because it
held reference to class factory. The same is not true with .NET, so, our
server sent WM_QUIT himself just after VB.NET release class factory, and
proxi object in vb.net had invalid reference from this moment. Thank you
once more.

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CreateObject failed with VB.Net, but succeded with VB6

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