Using COM to call C#.NET app from another framework?

Question

I have an old application that I am programming in. I have built a small application in C# that interacts with a database. I need call this from the old app using an object to pass back a value. I have set it up to perform this from the old app: eg. My call from the old app vgContact = OLEGet(vlFCObject,"GetFirmContact") What is the easiest way to call the C#.NET app and return the value? Writing a .NET wrapper? Bearing in mind I am new to COM and .NET A collegue tried the following but it only seems to work for his PC alone. ============================================= using System; using System.Runtime.InteropServices; using Firm_Contact; namespace FirmContactCOM { [Guid("D6F88E95-8A27-4ae6-B6DE-0542A0FC7039")] [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface _FirmContact { [DispId(1)] int GetFirmContact(); } [Guid("13FE32AD-4BF8-495f-AB4D-6C61BD463EA4")] [ClassInterface(ClassInterfaceType.None)] [ProgId("FirmContactCOM.FirmContact")] public class FirmContact : _FirmContact { public FirmContact(){} public int GetFirmContact() { return(Firm_Contact.MainFirmContact.StartUp()); } } }