Clean out/replace invalid XML characters in element attributes

Question

UPDATE: The invalid characters are actually in the attributes instead of the elements, this will prevent me from using the CDATA solution as suggested below.

In my application I receive the following XML as a string. There are a two problems with this why this isn't accepted as valid XML. Hope anyone has a solution for fixing these bug gracefully.

There are ASCII characters in the XML that aren't allowed. Not only the one displayed in the example but I would like to replace all the ASCII code with their corresponding characters.
Within an element the '<' exists - I would like to remove all these entire 'inner elements' (<L CODE="C01">WWW.cars.com</L>) from the XML.

<?xml version="1.0" encoding="ISO-8859-1"?>
<cars>
  <car model="ford" description="Argentini&#235; love this"/>
  <car model="kia" description="a small family car"/>
  <car model="opel" description="great car <L CODE=&#034;C01&#034;>WWW.cars.com</L>"/>
</cars>

Ideally you should tell the person who gave this to you that they need to produce well-formed XML in the first place. The literal <s in embedded data should be < and the >s should be >. — Joe White
– Joe White, Commented Oct 13, 2011 at 15:11

Joe White · Accepted Answer · 2011-10-14 16:20:00Z

For a quick fix, you could load this not-XML into a string, and add [CDATA][1] markers inside any XML tags that you know usually tend to contain invalid data. For example, if you only ever see bad data inside <description> tags, you could do:

var soCalledXml = ...;
var xml = soCalledXml
    .Replace("<description>", "<description><![CDATA[")
    .Replace("</description>", "]]></description>");

This would turn the tag into this:

<description><![CDATA[great car <L CODE=&#034;C01&#034;>WWW.cars.com</L>]]></description>

which you could then process successfully -- it would be a <description> tag that contains the simple string great car <L CODE="C01">WWW.cars.com</L>.

If the <description> tag could ever have any attributes, then this kind of string replacement would be fraught with problems. But if you can count on the open tag to always be exactly the string <description> with no attributes and no extra whitespace inside the tag, and if you can count on the close tag to always be </description> with no whitespace before the >, then this should get you by until you can convince whoever is producing your crap input that they need to produce well-formed XML.

Update

Since the malformed data is inside an attribute, CDATA won't work. But you could use a regular expression to find everything inside those quote characters, and then do string manipulation to properly escape the <s and >s. They're at least escaping embedded quotes, so a regex to go from " to " would work.

Keep in mind that it's generally a bad idea to use regexes on XML. Of course, what you're getting isn't actually XML, but it's still hard to get right for all the same reasons. So expect this to be brittle -- it'll work for your sample input, but it may break when they send you the next file, especially if they don't escape & properly. Your best bet is still to convince them to give you well-formed XML.

using System.Text.RegularExpressions;

var soCalledXml = ...;
var xml = Regex.Replace(soCalledXml, "description=\"[^\"]*\"",
    match => match.Value.Replace("<", "&lt;").Replace(">", "&gt;"));

Hi Joe, i made a mistake because the illegal xml characters are actually part of the attributes instead of the elements. A car element has no sub elements but everything as a attribute. This renders out the CDATA solution. Do you know anything else?

pakopa · Accepted Answer · 2011-10-13 15:22:41Z

0

You could wrap that content in a CDATA section.

With regex it will be something like this, match

"<description>(.*?)</description>"

and replace with

"<description><![CDATA[$1]]></description>"

answered Oct 13, 2011 at 15:22

pakopa

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