A C# Combinations Iterator

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

namespace Combinations
{
    class Program
    {
        static void Main(string[] args)
        {
            string line, s;
            int count;
            do
            {
                Console.WriteLine("Select Demo:");
                Console.WriteLine("1 - Combinations over integers.");
                Console.WriteLine("2 - Combinations over a string.");
                Console.WriteLine("3 - Combinations and permutations.");
                Console.WriteLine("q - Quit.");
                line = Console.ReadLine();
                if (line == "q") break;
                switch (line)
                {
                    case "1":
                        CombinationsOverIntegers();
                        break;
                    case "2":
                        if (!InputParameters(out s, out count))
                            continue;
                        CombinationsOverString(s, count);
                        break;
                    case "3":
                        if (!InputParameters(out s, out count))
                            continue;
                        CombinationsPermutations(s, count);
                        break;
                }
            } while (line != "q");
        }

        private static bool InputParameters(out string s, out int count)
        {
            Console.WriteLine("Enter string:");
            s = Console.ReadLine();
            Console.WriteLine("How may characters to choose?");
            if (!int.TryParse(Console.ReadLine(), out count)) return false;
            return true;
        }

        private static void CombinationsPermutations(string s, int count)
        {
            foreach (var comb in Iterator.Combinations(s.ToCharArray().ToList(), count))
            {
                foreach (var perm in Iterator.Permutations(comb, count))
                {
                    string r = new string(perm.Take(count).ToArray());
                    Console.Write("{0,-8}", r);
                }
            }
            Console.WriteLine();
        }

        private static void CombinationsOverString(string s, int count)
        {
            foreach (var comb in Iterator.Combinations(s.ToCharArray().ToList(), count))
            {
                string r = new string(comb.Take(count).ToArray());
                Console.Write("{0,-8}", r);
            }
            Console.WriteLine();
        }

        private static void CombinationsOverIntegers()
        {
            List<int> l = new List<int>() { 1, 2, 3, 4, 5, 6 };
            int count = 4;
            foreach (var comb in Iterator.Combinations(l, count))
            {
                string s = comb.Take(count).Aggregate<int, string>("", (x, y) => x + y);
                Console.Write("{0,-8}", s);
            }
            Console.WriteLine();
        }
    }
}