C method of encrypting letters or numbers into letters

This article shows an example of how C# encrypts letters or numbers into letters. Share to everybody for everybody reference. Specific implementation methods are as follows:

public class MD5

{

        static List<KeyValuePair<char, char>> MappingList;

        #region  encryption       public static string Encrypt(string str)

        /// <summary>

        ///  encryption 

        /// </summary>

        /// <param name="str"> The string to encrypt </param>

        /// <returns> The string that returns the result </returns>

        public static string Encrypt(string str)

        {

            MappingList = new List<KeyValuePair<char, char>>();

            for (char c = '0'; c <= '9'; c++)

                MappingList.Add(new KeyValuePair<char, char>(c, (char)(c - '0' + 'a')));

            for (char c = 'a'; c <= 'f'; c++)

                MappingList.Add(new KeyValuePair<char, char>(c, (char)(c - 'a' + 'u')));

            return Encoding.ASCII.GetBytes(str)

                .Select((b, i) => (b ^ ((byte)(0xa0 + i))).ToString("x2"))

                .Aggregate("", (s, c) => s + c)

                .ToCharArray().Select(c => MappingList.First(kv => kv.Key == c).Value)

                .Aggregate("", (s, c) => s + c);

        } 

        #endregion

        #region  decryption        public static string Decrypt(string str)

        /// <summary>

        ///  decryption 

        /// </summary>

        /// <param name="str"> Decrypted string </param>

        /// <returns> Return result string </returns>

        public static string Decrypt(string str)

        {

            string base16 = str.ToCharArray()

                .Select(c => MappingList.First(kv => kv.Value == c).Key)

                .Aggregate("", (s, c) => s + c);

            return Encoding.ASCII.GetString((new byte[base16.Length / 2])

                .Select((b, i) => (byte)(Convert.ToByte(base16.Substring(i * 2, 2), 16) ^ ((byte)(0xa0 + i)))).ToArray());

        } 

        #endregion

}

Hopefully this article has helped you with your C# programming.