C# hexadecimal value 0x12, is an invalid character

c# regex replace xmldocument
Duke picture Duke · Jan 10, 2014 · Viewed 59.8k times · Source

I am loading a lot of xml documents and some of them return errors like "hexadecimal value 0x12, is an invalid character" and there are different character. How to remove them?

Answer

Duke picture Duke · Jan 10, 2014

I made a small research here.

Here is the ASCII table. There are 128 symbols asciitable Here is some small test code which adds every symbol from ASCII table and tries to load it as an XML document.

static public void RegexTry()
{
    StreamReader stream = new StreamReader(@"test.xml");
    string xmlfile = stream.ReadToEnd();
    stream.Close();

    string text = "";

    for (int i = 0; i < 128; i++ )
    {
        char t = (char) i;

        text = xmlfile.Replace('П', t);

        XmlDocument xml = new XmlDocument();
        try
        {
            xml.LoadXml(text);
        }
        catch (Exception ex)
        {
            Console.WriteLine("Char("+i.ToString() +"): " + t + " => error! " + ex.Message);
            continue;
        }

        Console.WriteLine("Char(" + i.ToString() + "): " + t + " => fine!");
    }

    Console.ReadKey();
}

As a result it returns:

Char(0): => error! '.', hexadecimal value 0x00, is an invalid character. Line 5, position 7.
Char(1): => error! '', hexadecimal value 0x01, is an invalid character. Line 5, position 7.
Char(2): => error! '', hexadecimal value 0x02, is an invalid character. Line 5, position 7.
Char(3): => error! '', hexadecimal value 0x03, is an invalid character. Line 5, position 7.
Char(4): => error! '', hexadecimal value 0x04, is an invalid character. Line 5, position 7.
Char(5): => error! '', hexadecimal value 0x05, is an invalid character. Line 5, position 7.
Char(6): => error! '', hexadecimal value 0x06, is an invalid character. Line 5, position 7.
Char(7): => error! '', hexadecimal value 0x07, is an invalid character. Line 5, position 7.
Char(8): => error! '', hexadecimal value 0x08, is an invalid character. Line 5, position 7.
Char(9):     => fine!
Char(10): 
 => fine!
Char(11): => error! '', hexadecimal value 0x0B, is an invalid character. Line 5, position 7.
Char(12): => error! '', hexadecimal value 0x0C, is an invalid character. Line 5, position 7.
Char(13): 
 => fine!
Char(14): => error! '', hexadecimal value 0x0E, is an invalid character. Line 5, position 7.
Char(15): => error! '', hexadecimal value 0x0F, is an invalid character. Line 5, position 7.
Char(16): => error! '', hexadecimal value 0x10, is an invalid character. Line 5, position 7.
Char(17): => error! '', hexadecimal value 0x11, is an invalid character. Line 5, position 7.
Char(18): => error! '', hexadecimal value 0x12, is an invalid character. Line 5, position 7.
Char(19): => error! '', hexadecimal value 0x13, is an invalid character. Line 5, position 7.
Char(20): => error! '', hexadecimal value 0x14, is an invalid character. Line 5, position 7.
Char(21): => error! '', hexadecimal value 0x15, is an invalid character. Line 5, position 7.
Char(22): => error! '', hexadecimal value 0x16, is an invalid character. Line 5, position 7.
Char(23): => error! '', hexadecimal value 0x17, is an invalid character. Line 5, position 7.
Char(24): => error! '', hexadecimal value 0x18, is an invalid character. Line 5, position 7.
Char(25): => error! '', hexadecimal value 0x19, is an invalid character. Line 5, position 7.
Char(26): => error! '', hexadecimal value 0x1A, is an invalid character. Line 5, position 7.
Char(27): => error! '', hexadecimal value 0x1B, is an invalid character. Line 5, position 7.
Char(28): => error! '', hexadecimal value 0x1C, is an invalid character. Line 5, position 7.
Char(29): => error! '', hexadecimal value 0x1D, is an invalid character. Line 5, position 7.
Char(30): => error! '', hexadecimal value 0x1E, is an invalid character. Line 5, position 7.
Char(31): => error! '', hexadecimal value 0x1F, is an invalid character. Line 5, position 7.
Char(32):   => fine!
Char(33): ! => fine!
Char(34): " => fine!
Char(35): # => fine!
Char(36): $ => fine!
Char(37): % => fine!
Char(38): => error! An error occurred while parsing EntityName. Line 5, position 8.
Char(39): ' => fine!
Char(40): ( => fine!
Char(41): ) => fine!
Char(42): * => fine!
Char(43): + => fine!
Char(44): , => fine!
Char(45): - => fine!
Char(46): . => fine!
Char(47): / => fine!
Char(48): 0 => fine!
Char(49): 1 => fine!
Char(50): 2 => fine!
Char(51): 3 => fine!
Char(52): 4 => fine!
Char(53): 5 => fine!
Char(54): 6 => fine!
Char(55): 7 => fine!
Char(56): 8 => fine!
Char(57): 9 => fine!
Char(58): : => fine!
Char(59): ; => fine!
Char(60): => error! The '<' character, hexadecimal value 0x3C, cannot be included in a name. Line 5, position 13.
Char(61): = => fine!
Char(62): > => fine!
Char(63): ? => fine!
Char(64): @ => fine!
Char(65): A => fine!
Char(66): B => fine!
Char(67): C => fine!
Char(68): D => fine!
Char(69): E => fine!
Char(70): F => fine!
Char(71): G => fine!
Char(72): H => fine!
Char(73): I => fine!
Char(74): J => fine!
Char(75): K => fine!
Char(76): L => fine!
Char(77): M => fine!
Char(78): N => fine!
Char(79): O => fine!
Char(80): P => fine!
Char(81): Q => fine!
Char(82): R => fine!
Char(83): S => fine!
Char(84): T => fine!
Char(85): U => fine!
Char(86): V => fine!
Char(87): W => fine!
Char(88): X => fine!
Char(89): Y => fine!
Char(90): Z => fine!
Char(91): [ => fine!
Char(92): \ => fine!
Char(93): ] => fine!
Char(94): ^ => fine!
Char(95): _ => fine!
Char(96): ` => fine!
Char(97): a => fine!
Char(98): b => fine!
Char(99): c => fine!
Char(100): d => fine!
Char(101): e => fine!
Char(102): f => fine!
Char(103): g => fine!
Char(104): h => fine!
Char(105): i => fine!
Char(106): j => fine!
Char(107): k => fine!
Char(108): l => fine!
Char(109): m => fine!
Char(110): n => fine!
Char(111): o => fine!
Char(112): p => fine!
Char(113): q => fine!
Char(114): r => fine!
Char(115): s => fine!
Char(116): t => fine!
Char(117): u => fine!
Char(118): v => fine!
Char(119): w => fine!
Char(120): x => fine!
Char(121): y => fine!
Char(122): z => fine!
Char(123): { => fine!
Char(124): | => fine!
Char(125): } => fine!
Char(126): ~ => fine!
Char(127):  => fine!

You can see there are a lot of symbols which can't be in XML code. To replace them we can use Reqex.Replace 

static string ReplaceHexadecimalSymbols(string txt)
{
    string r = "[\x00-\x08\x0B\x0C\x0E-\x1F\x26]";
    return Regex.Replace(txt, r,"",RegexOptions.Compiled);
}

PS. Sorry if everybody knew that.

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