using System;

    using System.Collections.Generic;

    using System.ComponentModel;

    using System.Linq;

    using System.Text;

​

    public class Program

    {

        static Dictionary<char, string> wordMap = new Dictionary<char, string>();

        static Dictionary<string, char> charMap = new Dictionary<string, char>();

​

        public static void InitializeLookups()

        {

            charMap = new Dictionary<string, char>

            {

                {"alpha", 'a'},{"beta",'Y'},{"gamma", 'g'},{"delta", '='}

            };

​

            wordMap = charMap.ToDictionary(e => e.Value, e => e.Key);

        }

​

        public static string ConvertCharToWords(string chars)

        {

            var strings = chars

                  .Select(c =>

                  {

                      string word;

                      if (!wordMap.TryGetValue(c, out word))

                          word = c.ToString();

                      return word;

                  });

            return string.Join(" ", strings);

        }

        public static string ConvertWordsToChars(string words)

        {

            var strings = words.Split(' ')

                  .Select(c =>

                  {

                      char character;

                      if (!charMap.TryGetValue(c, out character))

                          character = 'X';

                      return character;

                  });

            return string.Join("", strings);

        }

​

        public static void Main(string[] args)

        {

            InitializeLookups();

            string chars = ConvertWordsToChars("alpha beta gamma delta");

​

            Console.WriteLine(chars);

        }

    }