Create interface for your COM-visible class and implementation class:

using System;
using System.Runtime.InteropServices;

namespace MyNs {
// ...

[ComVisible(true), GuidAttribute("D541C809-198A-42ad-BB2F-E04C93AE7BFB")]
public interface IMyInterface {
    string ReturnSomething();
}

[ComVisible(true), GuidAttribute("1070C8DB-7D3A-4582-A071-5CC40815A319")]
public class MyClass : IMyInterface {
    public string ReturnSomething() {
        return "Hello world";
    }
}

// ...
}

Compile assembly, next create type library and register COM with regasm
tool:

regasm MyAssembly.dll /codebas /tlb:MyAssembly.tlb

And then you can use it with late-bind from VB 6:

dim myClass as object
set myClass = CreateObject("MyNs.MyClass");
dim returnValue as string
returnValue = myClass.ReturnSomething()

or reference it to your project and use it with early binding...

Zdenek D.