Update to my generator v1 nhs number generator

I am trying to update my NHs number generator for the current version of the data generator but the generator tool refuses to recognise my module. It has been placed in C:\Program Files (x86)\Red Gate\SQL Data Generator 2\Generators and compiled to DotNet2.
Is there anything I have done wrong in the code below? The code is a simple class library initially based on the Basic library but when that didn't work either, used elements of the full example.
I originally posted this in http://www.red-gate.com/messageboard/vi ... hp?t=10953 a few years ago...

Thanks
Jon

using System;
using System.Collections;
using System.Globalization;
using RedGate.SQLDataGenerator.Engine.Generators; 
using RedGate.SQLDataGenerator.Engine.Generators.Static;
using RedGate.SQLDataGenerator.Engine.Generators.Support;

namespace NHS 
{
     [Generator(typeof(int), "Generic", "NHS Number", "A valid check digited NHS number")]
    public class NhsNumberGenerator : GeneratorBase, IUniqueableGenerator
    {
         private Random _random; 

        // public int Seed { get; set; }
         public bool Unique { get; set; }

        public NhsNumberGenerator(GeneratorParameters parameters) :base(parameters)
        { 
          
        }

         public override IEnumerator GetNonNullEnumerator(GenerationSession session) 
        {
            while (true)
                yield return GenerateNhsNumber();
        } 

        private bool StandardNhsTest(string nhsNumberToTest) 
        { 
            var calcResult = 0; 
            var returnValue = true; 

            // Remove any spaces if number is in 3 3 4 format 
            nhsNumberToTest = nhsNumberToTest.Replace(" ", string.Empty); 

            // Simple validation 
            if (nhsNumberToTest.Length != 10) 
                // Only 10 characters allowed 
                returnValue = false; 
            else if (!IsNumeric(nhsNumberToTest)) 
                // is numeric 
                returnValue = false; 
            else if (",0000000000,1111111111,2222222222,3333333333,4444444444,5555555555,6666666666,7777777777,8888888888,9999999999".Contains(nhsNumberToTest)) 
                // Make sure no consecutive numbers 
                returnValue = false; 

            if (returnValue) 
            { 
                // Step 1 - add the numbers multiplied by their weighting 
                for (int digitIndex = 0; digitIndex < 9; digitIndex++) 
                { 
                    calcResult += Convert.ToInt32(nhsNumberToTest.Substring(digitIndex, 1)) * (10 - digitIndex); 
                } 

                // Step 2 Mod 11 calcuation to get remainder 
                calcResult = calcResult % 11; 

                // Step 3 - take remainder from 11 to give check digit 
                calcResult = 11 - calcResult; 
                if (calcResult == 11) 
                { 
                    calcResult = 0; 
                } 

                // Test calculated check digit against real digit 
                if (Convert.ToInt32(nhsNumberToTest.Substring(9, 1)) != calcResult) 
                { 
                    returnValue = false; 
                } 
            } 
            return returnValue; 
        } 
        /// <summary> 
        /// Helper function to generate valid NHS numbers. 
        /// </summary> 
        /// <returns></returns> 
        private string GenerateNhsNumber() 
        {
            if (_random == null) _random = new Random(Seed); 
            
            var calcResult = 0; 

            var nhsNumberToTest = _random.Next(100000000, 999999998).ToString(CultureInfo.InvariantCulture); 

            // Step 1 - add the numbers multiplied by their weighting 
            for (var digitIndex = 0; digitIndex < 9; digitIndex++)
                calcResult += Convert.ToInt32(nhsNumberToTest.Substring(digitIndex, 1))*(10 - digitIndex);

            // Step 2 Mod 11 calcuation to get remainder 
            calcResult = calcResult % 11; 

            // Step 3 - take remainder from 11 to give check digit 
            calcResult = 11 - calcResult; 
            if (calcResult == 11) 
                calcResult = 0; 
            else if (calcResult >= 10)  // If >10 is an invalid number so generate another 
                nhsNumberToTest = GenerateNhsNumber(); 
            else 
                nhsNumberToTest += calcResult.ToString(CultureInfo.InvariantCulture); 

            // Do a last sanity check to stop invalid checkdigit numbers coming through. 
            return StandardNhsTest(nhsNumberToTest) ? nhsNumberToTest : GenerateNhsNumber(); 
        } 

        /// <summary> 
        /// Determines whether the specified expression is numeric. 
        /// </summary> 
        /// <param name="expression">The expression.</param> 
        /// <returns> 
        ///    <c>true</c> if the specified expression is numeric; otherwise, <c>false</c>. 
        /// </returns> 
        private static Boolean IsNumeric(Object expression) 
        { 
            if (expression == null || expression is DateTime) 
                return false; 

            if (expression is Int16 || expression is Int32 || expression is Int64 || expression is Decimal || expression is Single || expression is Double || expression is Boolean) 
                return true; 

            try 
            { 
                if (expression is string) 
                    Double.Parse(expression as string); 
                else 
                    Double.Parse(expression.ToString()); 
                return true; 
            } 
            catch (FormatException)
            { } // just dismiss errors but return false 
            return false; 
        }
    } 

}