using C#'s XmlReader on slightly malformed XML

Question

I'm trying to use C#'s XmlReader on a large series of XML files, they are all properly formatted except for a few select ones (unfortunately I'm not in a position to have them changed, because it would break a lot of other code).

The errors only come from one specific part of the these affronting XML files and it's ok to just skip them but I don't want to stop reading the rest of the XML file.

The bad parts look like this:

 <InterestingStuff>
  ...
    <ErrorsHere OptionA|Something = "false" OptionB|SomethingElse = "false"/>
    <OtherInterestingStuff>
    ...
    </OtherInterestingStuff>
</InterestingStuff>

So really if I could just ignore invalid tags, or ignore the pipe symbol then I would be ok.

Trying to use XmlReader.Skip() when I see the name "ErrorsHere" doesn't work, apparently it already reads a bit ahead and throws the exception.

TLDR: How do I skip so I can read in the XML file above, using the XmlReader?

Edit:

Some people suggested just replacing the '|'-symbol, but the idea of XmlReader is to not load the entire file but only traverse parts you want, since I'm reading directly from files I can not afford the read in entire files, replace all instances of '|' and then read parts again :).

replacing | sign before loading a reader with - could solve the problem — Prashant Lakhlani
How are you reading the info into the XmlReader? Are you reading from stream? — Jethro
if you know the error in advance, can't you patch the content of the source before parsing it ? But in a general manner, you should correct the source xml.... or don't call it XML (I imagine you are dependant of someone else... ?) — Steve B
Good suggestions, but I don't want to read in the entire file (hence why I use XmlReader and not XmlDocument.Load()) because this could be costly and I don't need all the info in the files. To clarify I read directly from disk using XmlReader.Creat(filepath) and yes I'm depending on other people, so I can't do anything about the source. — Roy T.
+1 Steve B - XmlReader reads Xml, so convert the non-Xml input to valid Xml in an isolated method, keeping the rest of your code clean. — C.Evenhuis

Henk Holterman Henk Holterman · Accepted Answer · 2011-07-11T11:27:29

I've experimented a bit with this in the past.

In general the input simply has to be well-formed. An XmlReader will go into an unrecoverable error-state when the basic XML rules are broken. It is easy to avoid schema-validation but that's not relevant here.

Your only option is to clean the input, that can be done in a streaming manner (custom Stream or TextReader) but that will require a light form of parsing. If you don't have pipe-symbols in valid positions it's easy.

using C#'s XmlReader on slightly malformed XML

3 Answers