Accessing underlying managed object through a COM interface

Question

I have a third party assembly with a public abstract class implementing a certain COM interface. Something to the effect of

[ComVisible(true)]
public abstract class SomeClass: ISomeInterface
{
  ....
  public void Method1() {...}
}

The actual object is an internal object extending the SomeClass and is instantiated by the third party code

Is there a way to access public methods of this class if all I have is the CCW to the ISomeInterface?

To clarify my question:

I am building a flavored Visual Studio project extending the F# project system. Both my code and F# project system are managed, but there is a lot of unmanaged code between us. In my project manager I am getting a pointer (IntPtr) to the F# project manager and I can cast it to a number of interfaces F# project manager implements, but I need to call a (public) method on the project manager itself and so far I could not find a way to do that

Answer 1

Generally, no. You can only get at methods in this COM interface and other COM interfaces on the same object.