how to print all combination of n letter by vb.net language

using System;
using System.Collections.Generic;
using System.Linq;
 
namespace ConsoleApplication31
{
  class Program
  {
    static void Main(string[] args)
    {
      int[] test = new int[] { 1, 2, 4, 6 };
      int threshold = 10;
      foreach (var item in CombinationIndexes(test).Where(ii => ii.Sum(ix => test[ix]) >= threshold))
      {
        Console.WriteLine(string.Join(",", item.Select(i => i.ToString())));
      }
      Console.ReadLine();
    }
 
    const int BitsInUlong = 8 * sizeof(ulong);
    static IEnumerable<IEnumerable<int>> CombinationIndexes<T>(IList<T> collection)
    {
      if (collection.Count > BitsInUlong)
        throw new ArgumentOutOfRangeException("collection", "collection is too large");
      ulong count = (~(ulong)0) >> (BitsInUlong - collection.Count);
      for (ulong bits = 0; bits <= count; bits++)
      {
        yield return BitNumbers(bits);
      }
    }
 
    static IEnumerable<int> BitNumbers(ulong bits)
    {
      if (bits == 0)
        yield break;
      ulong mask = 1;
      for (int i = 0; i < BitsInUlong; ++i)
      {
        if ((bits & mask) != 0)
        {
          yield return i;
        }
        mask <<= 1;
      }
    }
  }
}

Matt T Heffron

yield Return BitNumbers(bits)