My first COM import

Question

I have a .h file with the following declarations:

////////////////////////////////////////////////////////////////////////////////
// Syntek Plug-In Custom Control GUIDs.                                       //
////////////////////////////////////////////////////////////////////////////////
// {59DF6360-6F14-4472-82B6-6EAB971EEFAD}
DEFINE_GUID(CLSID_IStkCustomControl,
            0x59DF6360, 0x6F14, 0x4472, 0x82, 0xB6, 0x6E, 0xAB, 0x97, 0x1E, 0xEF, 0xAD);

// {59DF6361-6F14-4472-82B6-6EAB971EEFAD}
DEFINE_GUID(CLSID_IStkCustomControl_PropertyPage,
            0x59DF6361, 0x6F14, 0x4472, 0x82, 0xB6, 0x6E, 0xAB, 0x97, 0x1E, 0xEF, 0xAD);

// Custom Control Interfaces.
MIDL_INTERFACE("59DF6360-6F14-4472-82B6-6EAB971EEFAD")
IStkCustomControl : public IUnknown
{
public:
    virtual HRESULT STDMETHODCALLTYPE Get(PKSPROPERTY_STK_CUSTOM_CONTROL_S pStkCustomControl) = 0;
    virtual HRESULT STDMETHODCALLTYPE Set(PKSPROPERTY_STK_CUSTOM_CONTROL_S pStkCustomControl) = 0;
};

I would like to port the interface IStkCustomControl to C#. So far, I have this C# code:

Guid guid = new Guid(0x59df6360, 0x6f14, 0x4472, 0x82, 0xb6, 0x6e, 0xab, 0x97, 0x1e, 0xef, 0xad);
Type type = Type.GetTypeFromCLSID(guid); // line 2 
object obj = Activator.CreateInstance(type);

When executing line 2, I get the exception

Creating an instance of the COM component with CLSID {59DF6360-6F14-4472-82B6-6EAB971EEFAD} from the IClassFactory failed due to the following error: 80040202.

What's going wrong here?

UPDATE: I found out that the IStkCustomControl interface is implemented in a file called StkProp.ax. I've tried to run AxImp.exe StkProp.ax, but that gave me

AxImp Error: Error loading type library/DLL. (Exception from HRESULT: 0x80029C4A (TYPE_E_CANTLOADLIBRARY))

If you don't have a really good reason to write your own wrapper you should create an automatic wrapper. Either by importing a COM reference in Visual Studio or creating the wrapper by tlbimp.exe — Albin Sunnanbo
– Albin Sunnanbo, Commented Aug 18, 2011 at 12:08
Agreed; it's just that I can't find any .tlb file which contains IStkCustomControl (another mystery). — user181813
– user181813, Commented Aug 18, 2011 at 12:13
That's because it is not an automation compatible interface that derives from IDispatch. Which makes using it from a managed program perilous. You'll have to redeclare the COM interfaces in your C# code. — Hans Passant
– Hans Passant, Commented Aug 18, 2011 at 15:33

Seva Alekseyev · Accepted Answer · 2011-08-18 13:16:28Z

1

More often than not, the type info is embedded in the DLL that implements the object. Use OLEView to make sure. If so, then set up a COM reference to that DLL and use the auto wrapper.

Having the type info as standalone TLB file is so late nineties.

answered Aug 18, 2011 at 13:16

Seva Alekseyev

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