C# Com Interop class methods are not visible in VB6?

Question

I have created a C# Com Interop class in .NET and I have registered it appropriately on my dev machine as well as set Com-Visible to true in the assembly. However when I reference the library within my vb6 application I am able to see the library name, the class name but none of the methods or properties associated with them?

If anyone could please help me fix this problem, I have been stuck on it for quite a while!

Here is my class:

using System;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace VNDBUtils
{
public enum VNConstants : long
{
    cenMySQLDataStore = 32
}

[InterfaceType(ComInterfaceType.InterfaceIsDual)]
[Guid("CF4EFB82-6EE1-4A84-9CA9-07B135888B68")]
[ComVisible(true)]
public interface IVNSqlFormatter
{
    //Properties
    long DS_Type { get; set; }
    string DS_Query { get; set; }

    //Methods
    string Format_Entity(string strString);
    string MqStrMan_MakeStringEndWith(string strString, string strMatch);
    bool MqStrMan_StringEndsWith(string strString, string strMatch);
    string MqStrMan_MakeStringStartWith(string strString, string StrMatch);
    bool MqStrMan_StringStartsWith(string strString, string strMatch);
    string Right(string value, int length);
    string Left(string value, int maxLength);
    string Format_Value(string strString);
}



[ClassInterface(ClassInterfaceType.None)]
[Guid("3884D59D-AB76-41E7-82B6-21C66DBDCBF3")]
[ComVisible(true)]
public class VNSqlFormatter : IVNSqlFormatter
{

    private const string SQUARE_LEFT = "[";
    private const string SQUARE_RIGHT = "]";

    public long DS_Type { get; set; }
    public string DS_Query { get; set; }

    public string Format_Entity(string strString)
    {           
        strString = strString.Trim();

        if (DS_Type == (long)VNConstants.cenMySQLDataStore)
        {
            return strString;
        }
        else
        {
            return MqStrMan_MakeStringEndWith(MqStrMan_MakeStringStartWith(strString, SQUARE_LEFT), SQUARE_RIGHT);
        }

    }

    public string MqStrMan_MakeStringEndWith(string strString, string strMatch)
    {
        if (MqStrMan_StringEndsWith(strString, strMatch) == false)
        {
            return strString + strMatch;
        }
        else
        {
            return strString; 
        }

    }

    public bool MqStrMan_StringEndsWith(string strString, string strMatch)
    {
        return String.Equals(Right(strString, strMatch.Length), strMatch);

    }

    public string MqStrMan_MakeStringStartWith(string strString, string strMatch)
    {
        if (MqStrMan_StringStartsWith(strString, strMatch) == false)
        {
            return strMatch + strString;
        }
        else
        {
            return strString; 
        }
    }

    public bool MqStrMan_StringStartsWith(string strString, string strMatch)
    {
       return String.Equals(Left(strString, strMatch.Length), strMatch);
    }

    public string Right(string value, int length)
    {
        if (String.IsNullOrEmpty(value))
        {
            return String.Empty;
        }

        return value.Length <= length ? value : value.Substring(value.Length - length);
    }

    public string Left(string value, int maxLength)
    {
        if(String.IsNullOrEmpty(value))
        {
            return String.Empty; 
        }

        maxLength = Math.Abs(maxLength);
        return value.Length <= maxLength ? value : value.Substring(0, maxLength);
    }

    public string Format_Value(string strString)
    {
            return strString.Replace("'", "''");
    }

}

}

Answer 1

Discussion in comments lead to the following, the ProgId attribute was not set.

[ClassInterface(ClassInterfaceType.None)]
[Guid("3884D59D-AB76-41E7-82B6-21C66DBDCBF3")]
[ComVisible(true)]
[ProgId("VNDBUtils.VNSqlFormatter")]
public class VNSqlFormatter : IVNSqlFormatter
{
    /* implementation information */
}

Answer 2

Have you edited the AssemblyInfo.cs file?

Typically, this is the default:

// Setting ComVisible to false makes the types in this assembly not visible 
// to COM components.  If you need to access a type in this assembly from 
// COM, set the ComVisible attribute to true on that type.
[assembly: ComVisible(false)]

// The following GUID is for the ID of the typelib if this project is exposed to COM
[assembly: Guid("e2e2a417-bd3d-414d-97f9-91196ce1c63a")]

You would need to set the [assembly: ComVisible(false)] to true.