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

        public static byte[] DecodeHexString(String hexString)
        {
            if (hexString == null)
                throw new ArgumentNullException( "hexString" );
                    
            bool spaceSkippingMode = false;    
                    
            int i = 0;
            int length = hexString.Length;
            
            if ((length >= 2) &&
                (hexString[0] == '0') &&
                ( (hexString[1] == 'x') ||  (hexString[1] == 'X') ))
            {
                length = hexString.Length - 2;
                i = 2;
            }
            
            // Hex strings must always have 2N or (3N - 1) entries.
            
            if (length % 2 != 0 && length % 3 != 2)
            {
                throw new ArgumentException( Environment.GetResourceString( "Argument_InvalidHexFormat" ) );
            }                
                
            byte[] sArray;
                
            if (length >=3 && hexString[i + 2] == ' ')
            {
                spaceSkippingMode = true;
                    
                // Each hex digit will take three spaces, except the first (hence the plus 1).
                sArray = new byte[length / 3 + 1];
            }
            else
            {
                // Each hex digit will take two spaces
                sArray = new byte[length / 2];
            }
                
            int digit;
            int rawdigit;
            for (int j = 0; i < hexString.Length; i += 2, j++) {
                rawdigit = ConvertHexDigit(hexString[i]);
                digit = ConvertHexDigit(hexString[i+1]);
                sArray[j] = (byte) (digit | (rawdigit << 4));
                if (spaceSkippingMode)
                    i++;
            }
            return(sArray);    
        }
    }