Here s a simple project with only a few steps, to get you started.

C# code:

using System;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

[assembly:System.CLSCompliant(true)]
[assembly: ComVisible(true)]
// The following GUID is for the ID of the typelib if this project is exposed to COM
[assembly: Guid("7d9c5cd3-73d4-4ab1-ba98-32515256c0b0")]

namespace Cheeso.ComTests
{
    [Guid("7d9c5cd3-73d4-4ab1-ba98-32515256c0b1")]
    public class TestReply
    {
        public string salutation;
        public string name;
        public string time;
    }

    [Guid("7d9c5cd3-73d4-4ab1-ba98-32515256c0b2")]
    public class TestObj
    {
        // ctor
        public TestObj () {}

        public TestReply SayHello(string addressee)
        {
            return SayHello(addressee, "hello");
        }

        public TestReply SayHello(string addressee, string greeting)
        {
            string x = String.Format("{0}, {1}!", greeting, addressee);
            Console.WriteLine("{0}", x);

            TestReply r = new TestReply
            {
                salutation = greeting,
                name = addressee,
                time = System.DateTime.Now.ToString("u")
            };
            return r;
        }
    }
}

VBScript client code:

Function Main()
    Dim obj
    Dim reply
    set obj = CreateObject("Cheeso.ComTests.TestObj")
    Set reply = obj.SayHello("Evgeny")
    WScript.Echo "Reply at: " & reply.time
    Set reply = obj.SayHello_2("Evgeny", "wassup")
    WScript.Echo "Reply at: " & reply.time
End Function

Main

To build:

(produce your .snk file, once)
csc.exe /t:library /debug+ /keyfile:Foo.snk /out:TestObj.dll TestObj.cs
regasm /codebase TestObj.exe

Then just run the vbscript (through cscript.exe).

Once you get the basic thing working, you can tweak it, add GAC, make the typelib explicit, add an explicit ProgId, and so on.

ps: FYI, this example shows what happens with overloaded .NET methods on a class registered for interop. There s an implicit _2 (_3, _4, etc) appended to the method name.

Have you read this article: COM Interop Exposed

In the last page (3) of the article, there s a list:

1. Define a .NET Interface for the methods you want to expose to COM.
2. Assign a GUID to that interface with the "Guid" attribute.
3. Have your class implement your interface as the first interface.
4. Assign a GUID to that class with the "Guid" attribute.
5. Add the "ClassInterface(ClassInterfaceType.None)" attribute to prevent regasm/tlbexp from creating an empty default interface.
6. Hard-code a specific version number in your AssemblyVersion attribute.
7. Create a strong-name key pair for your assembly and point to it via the AssemblyKeyFile attribute.
8. Add your assembly to the GAC,
9. Register your assembly for COM by using the REGASM command along with the "/tlb" option to generate a COM type library.

I m not sure if the GAC and ClassInterfaceType.None are the missing pieces of your puzzle, you might want to give it a try. Good luck!

There isn t anything really wrong with your code and you followed the correct install procedure, by the sound of it. The error code you get however clearly indicates that the script interpreter has trouble locating or loading the assembly. The best way to troubleshoot this is with SysInternals ProcMon utility.

I ran your code without trouble, these were the most relevant entries in the ProcMon log:

22  12:04:41.1795038 PM WScript.exe 55280   RegOpenKey  HKCRTTTTTT.FFFFF.CCCCCCCCC SUCCESS Desired Access: Read
26  12:04:41.1795682 PM WScript.exe 55280   RegOpenKey  HKCRTTTTTT.FFFFF.CCCCCCCCCCLSID   SUCCESS Desired Access: Read
29  12:04:41.1796996 PM WScript.exe 55280   RegQueryValue   HKCRTTTTTT.FFFFF.CCCCCCCCCCLSID(Default) SUCCESS Type: REG_SZ, Length: 78, Data: {3EB62C37-79BC-44F7-AFBD-7B8113D1FD4F}
34  12:04:41.1797653 PM WScript.exe 55280   RegOpenKey  HKCRCLSID{3EB62C37-79BC-44F7-AFBD-7B8113D1FD4F}   SUCCESS Desired Access: Read
62  12:04:41.1802539 PM WScript.exe 55280   RegOpenKey  HKCRCLSID{3EB62C37-79BC-44F7-AFBD-7B8113D1FD4F}InprocServer32    SUCCESS Desired Access: Read
71  12:04:41.1804181 PM WScript.exe 55280   RegQueryValue   HKCRCLSID{3EB62C37-79BC-44F7-AFBD-7B8113D1FD4F}InprocServer32(Default)  SUCCESS Type: REG_SZ, Length: 24, Data: mscoree.dll
824 12:04:41.2425662 PM WScript.exe 55280   RegQueryValue   HKCRCLSID{3EB62C37-79BC-44F7-AFBD-7B8113D1FD4F}InprocServer321.0.0.0CodeBase   SUCCESS Type: REG_SZ, Length: 124, Data: file:///c:/projects/ClassLibrary2/obj/Debug/ClassLibrary2.DLL
... Lots of .NET keys...
1239    12:04:41.2970169 PM WScript.exe 55280   CreateFile  C:projectsClassLibrary2objDebugClassLibrary2.dll   SUCCESS Desired Access: Read Attributes, Disposition: Open, Options: Open Reparse Point, Attributes: n/a, ShareMode: Read, Write, Delete, AllocationSize: n/a, OpenResult: Opened

To make Cheeso s example work on a 64-bit platform, make sure you invoke CScript.exe as:

%windir%SysWOW64cscript.exe test.vbs

Reference: Cannot use CreateObject from VB scripts on Windows 7 x64

May be, all of your problems are caused by VS. Try to compile your library from the command line by typing

csc.exe /t:library AClass.cs /keyfile:Foo.snk - produce your key file with VS!
regasm /codebase /tlb AClass.dll

VS are adding some stuff like /warn: /noconfig and so on, and also it adding references to another assemblies like System.Core and so on, and sometimes causes the erros. For me, compiling from csc worked.