System.Security.Util.Hex.ConvertHexDigit C# (CSharp) Method

        public static int ConvertHexDigit(Char val)
        {
            if (val <= '9' && val >= '0')
                return (val - '0');
            else if (val >= 'a' && val <= 'f')
                return ((val - 'a') + 10);
            else if (val >= 'A' && val <= 'F')
                return ((val - 'A') + 10);
            else
                throw new ArgumentException( Environment.GetResourceString( "ArgumentOutOfRange_Index" ) );  
        }

        // Token: 0x06002B0B RID: 11019 RVA: 0x0009FB40 File Offset: 0x0009DD40
        public static byte[] DecodeHexString(string hexString)
        {
            if (hexString == null)
            {
                throw new ArgumentNullException("hexString");
            }
            bool flag = false;
            int  i    = 0;
            int  num  = hexString.Length;

            if (num >= 2 && hexString[0] == '0' && (hexString[1] == 'x' || hexString[1] == 'X'))
            {
                num = hexString.Length - 2;
                i   = 2;
            }
            if (num % 2 != 0 && num % 3 != 2)
            {
                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidHexFormat"));
            }
            byte[] array;
            if (num >= 3 && hexString[i + 2] == ' ')
            {
                flag  = true;
                array = new byte[num / 3 + 1];
            }
            else
            {
                array = new byte[num / 2];
            }
            int num2 = 0;

            while (i < hexString.Length)
            {
                int num3 = Hex.ConvertHexDigit(hexString[i]);
                int num4 = Hex.ConvertHexDigit(hexString[i + 1]);
                array[num2] = (byte)(num4 | num3 << 4);
                if (flag)
                {
                    i++;
                }
                i += 2;
                num2++;
            }
            return(array);
        }