Interface Prototypes


Jeff Gaines

I posted this to the interop group but no response so far, hope people
don't mind my asking here.

I have down-loaded and am trying to understand a MSFT sample "Windows API
Code Pack 1.1".

In one of the comments it says:
To successfully import a COM interface, all inherited methods need to be
declared again with the exception of those already declared in IUnknown".

None of my interface prototypes do this, I didn't know it was necessary!
Interestingly they still seem to work though.

Is this correct?

I found a contradiction when I created a class based on the
IExplorerBrowser interface. My prototype for IExplorerBrowser defined it
as inheriting from IUnknown (rightly or wrongly) and the compiler
complained that I hadn't implemented the prototypes of IUnknown in the

I would appreciate any comments or links so I can try and understand this
Is there a definitive source of C# interface prototypes? is
good but I'm not sure it's definitive.



Jeff Gaines

As far as definitive sources go, I would say MSDN is the definitive source.
Here's a good place to start:

Now that's a right riveting read :)
Thanks, Peter.

Without code and links to references you're using, it's hard to know
exactly what issues you may or may not be having. In general, a managed
COM interface has to declare all the members in the original COM interface,
and a managed COM implementation has to implement all the members in the
original COM interface. The exception for IUnknown exists because .NET
handles the AddRef/Release semantics on the COM side. It's been a few
years so I don't recall how QueryInterface is handled, but I have a vague
recollection that this is overridable in a custom implementation, where the
default behavior is that QI will only ever return the declared COM
interface implementation.

The Windows API Code pack is at:

I think, since it is MSFT code, I probably ought to update my own
definitions in line with MSFT's - or just use the dll it produces.

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