QueryInterface of out-of-proc COM server on interface imported from TLB

Question

I define my interfaces in an A.idl file, which I compile to A.tlb

In a VS2005 ATL project "B" I use importlib(A.tlb) in B.idl and #import "A.tlb" in stdafx.h and implement an interface IA from A.tlb in an ATL COM class. The project outputs a B.dll and a B.tlb

I add the B.tlb to refererences of a C# application and within the code I instantiate the COM object.

The instantiation works without problems if I use either

Type.GetTypeFromCLSID(); Activator.CreateInstance(...);

or

[DllImport("ole32.dll", ...)] CoCreateInstance(...)

Both work fine, the object instantiates and I can cast it to IA interface defined in A.tlb (actually a RCW generated from the tlb) and invoke its methods. Still no problems.

Then I use OLEView to enable the COM object activation using the default DllHost.exe surrogate.

The instantiation of the COM object within the surrogate (parameter CLSCTX_LOCAL_SERVER in CoCreateInstance) is still without problems, but when I try to cast the object to the IA interface defined in A.tlb I get E_NOINTERFACE and a message saying QueryInterface failed because "No such interface supported".

Please help. What could be wrong? If you need any additional info, I'll try to provide as much as possible.

Answer 1

You need to build and register the proxy/stub DLL. Required to marshal the interfaces across process boundaries. I can't find a great MSDN page for it, but it is mentioned here.