Expose types from embedded interop type to other assemblies

Question

I have an ATL COM library that defines an enum and an interface in MIDL like:

[uuid(65785D49-574A-4B1B-95F1-B9C7F283364A)]
typedef enum Options
{
    Option1,
    Option2
} Options;

[
    object,
    uuid(2E3D1B1A-DF95-434F-836B-73FF1245B608),
    oleautomation,
    nonextensible,
    pointer_default(unique)
]
interface IExample : IUnknown
{
    HRESULT Test([in] Options option, [out, retval] BSTR* str);
};

I then create a managed assembly and reference the TLB, which creates a PIA and embeds the types (Embed Interop Types = true) into the managed assembly.

In the managed assembly, I now create a class that implements the interface:

public class Example : IExample
{
    public string Test(Options option)
    {
        return option.ToString();
    }
}

Now I would like to create a third assembly that references the managed assembly and creates the object and call into it, but it doesn't let me since Options is an unreferenced type (requires me to include the PIA generated from the typelib):

public class Equivalence
{
    public void UseTest()
    {
        Example e = new Example();
        e.Test(Options.Option1);    // recognizes that it requires an ExampleLib.Options parameter, but that type isn't available
    }
}

Using reflector, I can see it inside the managed assembly, but it isn't viewable by object browser:

namespace ExampleLib
{
    [ComImport, CompilerGenerated, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("2E3D1B1A-DF95-434F-836B-73FF1245B608"), TypeIdentifier]
    public interface IExample

    [Guid("65785D49-574A-4B1B-95F1-B9C7F283364A"), CompilerGenerated, TypeIdentifier("15a6cf97-c415-4866-bdfb-7da65edb1faa", "ExampleLib.Options")]
    public enum Options
}

My managed assembly is itself a library intended to be distributed as an API, and I would like to expose this enumeration and interface so that it can be used by outside parties without having to deliver the PIA generated from the typelib of the ATL COM library. Is it possible?

Answer 1

Apparently this cannot be done. One of the errors (CS1748) pointed me to this post which says the PIA must be linked in by both assemblies.