How to call a .Net COM+ object from C++ functions library?

Question

I've not found some example that really works. I need to create an interaction system for MetaTrader. It's better to use modern technologies like WCF or somehting else using C#, but MetaTrader doesn't support COM or just OOP at all. So I need some gateway component that must be functions library with non-object interface. Surely, it requires usage of C++. But I'm not succeeded to find over the Web some example how to call from a C++ functions library a C# COM+ DLL. All the examples I could find use component C++ assemblies that are not supported by MetaTrader. So, I can't use namespace, etc. in C++. I wrote a COM+ server application that is easy to call from C# by the following lines

object c2 = Activator.CreateInstance(Type.GetTypeFromProgID("Imutome.COMPlusCache.Cache"));
c2.GetType().InvokeMember("OnTransfer", BindingFlags.InvokeMethod, null, c2, null);

But when I'm trying to write in C++ something like this

CLSIDFromProgID(OLESTR("Imutome.COMPlusCache.Cache"), &rclsid);
HRESULT hres = CoCreateInstance(rclsid, NULL, CLSCTX_LOCAL_SERVER, IID_IDispatch, (void **)&ppv);

I get just zeros in ppv and "0x80040154 Class not registered" in hres. I'm not sure what flags or what interface are required but I get the same error whatever I try. Although in C# everything works. Tell me please what do I need to change to make C++ succesfully create a COM+ object instance.

What happens if you pass CLSCTX_ALL? Also does CLSIDFromProgID() actually retrieve the right class id? — sharptooth
– sharptooth, Commented Mar 30, 2011 at 13:41
Have you initialized COM in the C++ thread? What about narrowing down the problem by trying to create some other more basic COM object using the same code (but a different ProgId, obviously). — mackenir
– mackenir, Commented Mar 30, 2011 at 13:45
(BTW depending on how you registered the C# assembly, it may need to be in the same directory as the running app) — mackenir
– mackenir, Commented Mar 30, 2011 at 13:46
@mackenir: He would have got another error code if he hadn't initialized COM. — sharptooth
– sharptooth, Commented Mar 30, 2011 at 13:48
CLSCTX_ALL doesn't help also. Of course, I've used CoInitialize before. The C# assembly is registered using ComponentService GUI. May be IID_IDispatch is really incorrect but I don't know what can I replace it with. ComponentService displays IManagedObject and other interfaces of ServicedComponent and one my inteface ICache. — user3536113
– user3536113, Commented Mar 30, 2011 at 14:52

Oleg · Accepted Answer · 2011-03-31 08:59:00Z

1

I believe the problem is in the way you register your component. You shoud use:

regasm your_component_name.dll /tlb /codebase

OR

regasm your_component_name.dll /tlb

AND put your component library to GAC or your executable location. Hope this helps. ComponentService GUI is not the same.

answered Mar 31, 2011 at 8:59

Oleg

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user3536113 Over a year ago

The problem is solved. The reason was really very simple. It was that the example from the Web I've used for the base had [assembly: AssemblyVersion("1.0.*")] So, the strong name didn't match the assembly version. I had just to replace the asteric.

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