Error in exposing c# DLL to VB6

Question

I would like to ask how will I properly exposed my C# DLL to vb6. The purpose of exposing the dll is to consume a WCF service for a VB6 Application since it cant consume directly the Wcf Service.

Below is the code in c#

[Guid("116CCA1E-7E39-4515-9849-90790DA6431E")]
[ClassInterface(ClassInterfaceType.None),ComSourceInterfaces(typeof(ITestBillerV10Service))]
[ComVisible(true)]
public class TestBillerV10 : ITestBillerV10Service
{
    TestBillerInquiry.TestBillerInquiryClient _TestBillerInquiry;

    public TestBillerV10()
    {
        _TestBillerInquiry = new TestBillerInquiry.TestBillerInquiryClient();
        System.Net.ServicePointManager.Expect100Continue = false;
    }

    /// <summary>
    /// Inquire if account no is valid or not
    /// </summary>
    /// <param name="accountNo">Account No. to check</param>
    /// <param name="userId">User Id of the terminal</param>
    /// <returns>string array Index[0] = response Code(Yes/No), Index[1] = Description for Response, Index[2] = Error Code if response code is No</returns>
    [ComVisible(true)]
    [DispId(1)]
    public string[] Inquiry(string accountNo, string userId)
    {
        var newInquiry = new TestBillerInquiry.TestBillerInquiryRequest {AccountNumber = accountNo, UserId= userId };
        TestBillerInquiry.TestBillerInquiryResponse response = _TestBillerInquiry.Inquiry(newInquiry);
        var retVal = new string[3];
        retVal[0] = response.Response;
        retVal[1] = response.Message;
        retVal[2] = response.Error;
        return retVal;
    }
}

and simple interface below

/// <summary>
    /// Inquire if account no is valid or not
    /// </summary>
    /// <param name="accountNo">Account No. to check</param>
    /// <param name="userId">User Id of the terminal</param>
    /// <returns>string array Index[0] = response Code(Yes/No), Index[1] = Description for Response, Index[2] = Error Code if response code is No</returns>
    [ComVisible(true)]
    public interface ITestBillerV10Service
    {
        [DispId(1)]
        string[] Inquiry(string accountNo, string userId);
    }

Below is how I try to consume it on vb6 but it returns a

runtime erro 429 which says Acvtive X component cant create object.

Dim testBillerV10 As V10Bridge.testBillerV10
Set testBillerV10 = New testBillerV10

Answer 1

Try 2 changes. First your class needs a ProgID attribute (and I don't use ComSourceInterfaces so I got rid of it):

[Guid("116CCA1E-7E39-4515-9849-90790DA6431E")]
[ClassInterface(ClassInterfaceType.None)]
[ComVisible(true)]
[ProgID("MyNameSpace.TestBillerV10")]
public class TestBillerV10 : ITestBillerV10Service

Your interface needs a Guid and InterfaceType :

[Guid("782AB14D-BE28-4b47-9498-DFF94B457E6D")]
[InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
[ComVisible(true)]
public interface ITestBillerV10Service