Registration-free COM client

[Thalamus via Digitalmars-d-learn]

Hi everyone,

I've succeeded in using D as a client for regular (registered) 
COM servers in the past, but in this case, I'm building the 
server as well. I would like to avoid registering it if possible 
so XCOPY-like deployment remains an option. Can a 
registration-free COM client be built in D? If so, how can the 
code be setup to consume the manifest file, or alternately, is 
there a way to just point D to the correct assembly directly in 
code?

Some background info:

The project I'm working on requires a high degree of D and C# 
interop. Getting C# to invoke D via C linkage is simple, but I've 
encountered a lot of problems the other way around.

Although it's technically possible to get pointers to C# objects 
such that the same approach could be used, doing so would require 
large portions of the code to be marked unsafe, the objects to be 
instantiated as fixed, use of GCHandle.Alloc, etc., which has a 
high dev learning curve and scalability issues.

The typical solution is to use delegates as callbacks. This 
works, but it doesn't scale well to more complex scenarios. You 
can send a struct of delegates to the D layer and use that to 
access public methods in a class, but if one of those methods 
would normally return a instance of a different class and the 
caller will need to invoke methods within that other class, this 
approach breaks down. For example, 
MyClassInstance.MyProperty.DoSomething() can't be modeled as 
MyClassInstanceDelegate.MyPropertyDelegate.DoSomethingDelegate(). 
This fails marshaling, because delegates are not blittable. 
There's very likely a way to structure complex delegate 
hierarchies that would in the end be marshalable, but the 
implementation and maintenance overhead would be sizable.

This leaves COM, which seems like it would work fine, on Windows 
anyway. (I'm not sure about Linux, but maybe some combo of Mono 
and WINE would do it? Not a high prio right now.) I'm hoping, 
though, to avoid having to register the C# COM server to keep 
things as simple as possible.

thanks!