Calling system provided COM object from WinRT component gives 'Class Not Registered' error

Question

I am writing a WinRT Component which creates a system provided COM object thru CoCreateInstance. Metro app successfully calls this WinRT object and underneath when winrt object calls CoCreateInstance, it will fail with Class Not Registered.

I have checked regedit, coclass is registered.

Any idea why?

Thanks

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CAT

Answer 1

Have you checked that the COM object you are trying to call into is one of the following:

http://msdn.microsoft.com/en-us/library/windows/apps/br205757(v=VS.85).aspx

Activation of certain COM objects is blocked at runtime,  as opposed to Win32 API which can be blocked at compile time by just marking the header appropriately.

Thanks
Raman 

Answer 2

I don't find the interface in the list, however before using COM server, is CoInitializeEx to be called from metro style app.

Thanks

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CAT

Answer 3

1. If your interface is not in the list, then you cannot call that API from Metro style app
2. No, you don't need to call CoInitializeEx from a C++ Metro style  app.  It is called implicitly for you at app startup time before any user code executes.

Thanks
Raman 

Answer 4

@Snekethan

What COM component were you after? If you can provide a scenario where this would be useful for a Metro style app, it would be useful feedback for us to hear for future consideration.

Thanks,

-David

Answer 5

it is 'PrinterConfig.dll', CLSID_PrinterExtensionManager.

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CAT

Answer 6

It appears that custom COM objects cannot be used naively from a Metro app. It appears that COM calls have to be made through a broker object and even from a custom WinRT component you cannot create an instance of you object unless the framework allows it. I see no way to extend the framework to do this and expect to see a not registered error if you try to do this (e.g., CoCreateInstance) from Metro. It would have been nice to be able to leverage the objects that are housed in desktop legacy servers and DLLs, but then there would be no way to control security and give the active metro app all the available resources in the system and limit power and CPU usage for the under lying background processes. If you need to do this then you will have to do it from a desktop app, which works fine in the cases that I have tested so far.