XML：仅对某些数据进行转义时如何进行预解析？

Question

XML snippet:

<field>&amp; is escaped</field>
<field>&quot;also escaped&quot;</field>
<field>is & "not" escaped</field>
<field>is &quot; and is not & escaped</field>

I'm looking for suggestions on how I could go about pre-parsing any XML to escape everything not escaped prior to running the XML through a parser?

I do not have control over the XML being passed to me, they likely won't fix it anytime soon, and I have to find a way to parse it.

The primary issue I'm running into is that running the XML as is into a parser, such as (below) will throw an exception due to the XML being bad due to some of it not being escaped properly

string xml = "<field>& is not escaped</field>";
XmlReader.Create(new StringReader(xml))

Answer 1

I'd suggest you use a Regex to replace un-escaped ampersands with their entity equivalent.

This question is helpful as it gives you a Regex to find these rogue ampersands:

&(?!(?:apos|quot|[gl]t|amp);|#)

And you can see that it matches the correct text in this demo . You can use this in a simple replace operation:

var escXml = Regex.Replace(xml, "&(?!(?:apos|quot|[gl]t|amp);|#)", "&");

And then you'll be able to parse your XML.

Answer 2

使用HTML Tidy将quote-ampersand设置为true来预处理文本数据（不是XML）。

Answer 3

If you want to parse something that isn't XML, you first need to decide exactly what this language is and what you intend to do with it: when you've written a grammar for the non-XML language that you intend to process, you can then decide whether it's possible to handle it by preprocessing or whether you need a full-blown parser.

For example, if you only need to handle an unescaped "&" that's followed by a space, and if you don't care about what happens inside comments and CDATA sections, then it's a fairly easy problem. If you don't want to corrupt the contents of comments or CDATA, or if you need to handle things like   when there's no definition of &npsp; , then life starts to become rather more difficult.

Of course, you and your supplier could save yourselves a great deal of time and expense if you wrote software that conformed to standards. That's what standards are for.