XML Exception: Invalid Character(s)

Question

I am working on a small project that is receiving XML data in string form from a long running application. I am trying to load this string data into an XDocument (System.Xml.Linq.XDocument), and then from there do some XML Magic and create an xlsx file for a report on the data.

On occasion, I receive the data that has invalid XML characters, and when trying to parse the string into an XDocument, I get this error.

[System.Xml.XmlException] Message: '?', hexadecimal value 0x1C, is an invalid character.

Since I have no control over the remote application, you could expect ANY kind of character.

I am well aware that XML has a way where you can put characters in it such as &#x1C or something like that.

If at all possible I would SERIOUSLY like to keep ALL the data. If not, than let it be.

---

I have thought about editing the response string programatically, then going back and trying to re-parse should an exception be thrown, but I have tried a few methods and none of them seem successful.

Thank you for your thought.

Code is something along the line of this:

TextReader  tr;
XDocument  doc;

string           response; //XML string received from server. 
... 
tr = new StringReader (response);   

try
{
    doc = XDocument.Load(tr);
}
catch (XmlException e)
{
    //handle here?
}

Answer 1

You can use the XmlReader and set the XmlReaderSettings.CheckCharacters property to false. This will let you to read the XML file despite the invalid characters. From there you can import pass it to a XmlDocument or XDocument object.

You can read a little more about in my blog.

To load the data to a System.Xml.Linq.XDocument it will look a little something like this:

XDocument xDocument = null;
XmlReaderSettings xmlReaderSettings = new XmlReaderSettings { CheckCharacters = false };
using (XmlReader xmlReader = XmlReader.Create(filename, xmlReaderSettings))
{
    xmlReader.MoveToContent();
    xDocument = XDocument.Load(xmlReader);
}

More information can be found here.

Answer 2

XML can handle just about any character, but there are ranges, control codes and such, that it won't.

Your best bet, if you can't get them to fix their output, is to sanitize the raw data you're receiving. You need replace illegal characters with the character reference format you noted.

(You can't even resort to CDATA, as there is no way to escape these characters there.)

Answer 3

Would something as described in this blog post be helpful?

Basically, he creates a sanitizing xml stream.