Someone

static public string Encode(string toEncode)
        {

            StringBuilder inStr = new StringBuilder(toEncode);
            StringBuilder outStr = new StringBuilder(toEncode.Length);
            char d;
            for (int i = 0; i < toEncode.Length; i++)
            {
                d = inStr[i];
                d = (char)(d ^ key);
                outStr.Append(d);
            }


            return outStr.ToString();

        }