Avoid COM marshalling

Question

I'm a little confused about com threading models.

I have an inproc server and I want to create an interface accesible from any thread regardless of the threading-model and/or flags used in CoInitializeEx.

When passing interfaces from one thread to another I use CoMarshalInterface/CoUnmarshalInterface without problems but I want to know if exists any way to avoid that and directly pass the interface pointer.

I tried making the interface use neutral apartment but still have to call CoMarshalInterface/CoUnmarshalInterface to avoid problems.

Regards, Mauro.

Answer 1

COM objects reside in one apartment only. Accessing a COM object via an interface pointer across apartment boundaries is never a good idea unless you're applicable scenario can utilize a free threaded marshaling aggregate. A free-threaded marshaller, essentially says that all clients of this interface, regardless of apartment and thread, are in the same process and will rely on the object itself to maintain synchronization and thread safety. The object itself must aggregate the free-threaded marshaller interface, so hopefully you're the author of it as well as the client code.

More information on free-threaded marshaling can be found at msdn.com, but one of their articles covering the object I tend to reuse again and again is this one.

I hope it helps you out.