public static string ParseHex(string hex)
        {
            char[] result = new char[hex.Length / 2];

            int hexIndex = 0;
            for (int i = 0; i < result.Length; i++)
            {
                result[i] = (char)(ParseHexDigit(hex[hexIndex++]) * 16 +
                ParseHexDigit(hex[hexIndex++]));
            }
            return new string(result);
        }

        static int ParseHexDigit(char c)
        {
            if (c >= '0' && c <= '9')
            {
                return c - '0';
            }
            if (c >= 'a' && c <= 'f')
            {
                return c - 'a' + 10;
            }
            if (c >= 'A' && c <= 'F')
            {
                return c - 'A' + 10;
            }
            throw new ArgumentException("Invalid hex character");
        }

@ http://blog.naver.com/mykojae?Redirect=Log&logNo=50080349024