Extension Method for building an Enumerator out of a .....

// Implemention idea based on the following article
// http://codingcraftsman.wordpress.com/2012/05/15/going-round-and-round/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace IterateUntilNull {

   //The "generic logic" for an iterator which returns null at the end of a "list"
   public class EnumeratorUntilNull<TIterator, TResult> where TIterator : class
   {
      public IEnumerable<TResult> Enumerator(TIterator iterator, Func<TIterator, TResult> func)
      {
         TResult next;
         do
         {
            next = func(iterator);
            if (next != null)
            {
               yield return next;
            }
         } while (next != null);
      }
   }

   // This is the base class for my finger exercise -> Random numbers a multiple of 1000 -> END
   public class IterateUntilNull {
      private Random r = new Random();

      public string GetNext() {
         int checkNumber = r.Next(10000);
         return (checkNumber%1000 == 0) ? null : checkNumber.ToString();
      }
   }

   // static extension method to inject the "Enumerator" into the base class
   public static class IterateUntilNullExtensions {
      public static IEnumerable<string> Enumerator(this IterateUntilNull iterator ) {
         return new EnumeratorUntilNull<IterateUntilNull, string>().Enumerator(iterator, (i) => i.GetNext());
      }
   }


   class Program {

      private static void Main(string[] args) {
         // The calling
         IterateUntilNull iun = new IterateUntilNull();
         foreach(var item in iun.Enumerator() ) {
            System.Console.WriteLine(item);
         }
         System.Console.ReadLine();
      }
   }
}