XPath Text Extraction

Question

0.00/5 (No votes)

See more:

Hi,

I have an XML file, and I need to extract some of its contents, however the file is non-standard XML and I am not familiar with XPath. I have tried researching on the internet however the presented solutions did not seem to work.

Basically the XML content of the file is as follows:

XML

<root xmlns="urn:schemas-upnp-org:device-1-0">
<specVersion>
<major>1</major>
<minor>0</minor>
</specVersion>
<URLBase>http://192.168.1.254:8000</URLBase>
<device>
<deviceType>
urn:schemas-upnp-org:device:InternetGatewayDevice:1
</deviceType>
<friendlyName>Name and Version here...</friendlyName>
<manufacturer>Name here...</manufacturer>
<manufacturerURL>Website here...</manufacturerURL>
<modelDescription>Internet Gateway Device</modelDescription>
<modelName>Model here...</modelName>
<modelNumber>Number here...</modelNumber>
<modelURL>URL here...</modelURL>
<serialNumber>Serial Number here...</serialNumber>
<UDN>uuid:UPnP_Name and MAC here...</UDN>
<presentationURL>/</presentationURL>
<serviceList>
<service>
<serviceType>urn:schemas-upnp-org:service:Layer3Forwarding:1</serviceType>
<serviceId>urn:upnp-org:serviceId:L3Forwarding1</serviceId>
<controlURL>/IGD/upnp/control/igd/layer3f</controlURL>
<eventSubURL>/IGD/upnp/event/igd/layer3f</eventSubURL>
<SCPDURL>/IGD/upnp/Layer3Forwarding.xml</SCPDURL>
</service>
</serviceList>
</device>
</root>

I need to extract the text in the deviceType and serviceType tags. I have tried using the "/deviceType" tag but it extracts nothing, while the "//*" seems to retrieve all the elements in the document, however that is not what I had in mind. Sorry to be bothering with possibly a very easy question, but I can't get it to work and I'm not sure which aspect I'm doing wrong. Any code snippets of this text extraction are greatly appreciated.

P.S. In the original XML document, there are multiple deviceType and serviceType tags and I need to extract them all, not just the first occurrence. Thanks.

Posted 2-Dec-12 21:48pm

Trapper-Hell

Updated 3-Dec-12 0:45am

v4

Add a Solution

2 solutions

Solution 1

Simple example is given over here[^]...

Posted 2-Dec-12 21:57pm

Krunal Rohit

Comments

Trapper-Hell 3-Dec-12 4:04am

I'd have preferred a more tailored solution rather than a link, however I have considered the submitted link and tried the following line of code:

XmlNode node = doc.SelectSingleNode("deviceType");

However the node variable is null.

[no name] 3-Dec-12 4:07am

How it could be possible ?? Try to put breakpoint over there and debug it..

Trapper-Hell 3-Dec-12 4:44am

I did place a breakpoint to go through the process but I'm not sure what I'm supposed to notice.

The code thus far is fairly simple:

------------

XmlDocument doc = new XmlDocument();
doc.Load("C:\\\\IGD.xml");

XmlNode node = doc.SelectSingleNode("deviceType");

------------

After going over the third line, the node variable remains null. I've tested that the doc is loaded fine and it would seem so, but it cannot select the tag. Could it be because the first line of the XML is non-standard XML ?

[no name] 3-Dec-12 4:45am

Are you getting error on first line or else ??

Trapper-Hell 3-Dec-12 4:47am

I am not getting any errors on the lines posted. It all seems to work fine, however the node variable remains null. So if I were to add a line like this afterwards:

string extension = node.ChildNodes[0].InnerText;

I'd get a NullReferenceExecption since the node variable remains null.

Trapper-Hell 3-Dec-12 4:56am

Can you possibly try the provided sample XML yourself to see if you can extract the text?

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

CPallini · Accepted Answer · 2012-12-03T00:17:00

Solution 2

You have to handle the namespace in your code, e.g.

C#

XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
      nsmgr.AddNamespace("x", "urn:schemas-upnp-org:device-1-0");
      string deviceType = doc.DocumentElement.SelectSingleNode("./x:device/x:deviceType", nsmgr).InnerText;

Please note the XML document you posted in invalid: there is a spurious deviceType closing tag near the end:

</serviceList>
</deviceType> <==== ERROR HERE
</device>
</root>

Posted 3-Dec-12 0:17am

CPallini

Comments

Trapper-Hell 3-Dec-12 6:50am

Great observation! I wrote the end tags myself since the true XML was too long, and I just extracted the important aspects of it. Please ignore the erroneous tag in the end (I revised it in the original post).

With regards to your proposed solution, it worked :D So I'm quite glad! Before I accept the solution, can you kindly explain why you had to add the namespace (and its importance)?

And finally, there are other <deviceType> tags that are children of other tags (under some branch under the <service> tag). Is it possible that I search for all <deviceType> tags irrelevant of their position within the document?

CPallini 3-Dec-12 7:58am

You have to add the namespace because the namespace attribute is inherited by all the children of the root node.

To select all the deviceType tags the way you depicted use the '//' in the XPath query, see
http://www.tizag.com/xmlTutorial/xpathdescendant.php

Trapper-Hell 3-Dec-12 8:09am

That about sums it all up :) Thank you for your time!

CPallini 3-Dec-12 8:28am

You are welcome.

Trapper-Hell 3-Dec-12 8:15am

Sorry to be bothering you again, but I tried the following code:

int deviceCounter = doc.DocumentElement.SelectNodes("./x:device//x:deviceType").Count;

However that gives an XPathException. What am I doing wrong here?

CPallini 3-Dec-12 8:30am

I don't know: your code gives me 1, on your original XML file.

Trapper-Hell 3-Dec-12 8:38am

XmlDocument doc = new XmlDocument();
doc.Load("C:\\\\xml.xml");

XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
nsmgr.AddNamespace("x", "urn:schemas-upnp-org:device-1-0");
string deviceType = doc.DocumentElement.SelectSingleNode("./x:device/x:deviceType", nsmgr).InnerText;
int deviceCounter = doc.DocumentElement.SelectNodes("./x:device//x:deviceType").Count;

That's the code I'm using the XML I submitted. It throws an XPath Exception with the following message: "Namespace Manager or XsltContext needed. This query has a prefix, variable, or user-defined function."

CPallini 3-Dec-12 9:15am

You must use the namespace manager nsmgr (like you did before), namely:
int deviceCounter = doc.DocumentElement.SelectNodes("./x:device//x:deviceType", nsmgr).Count;

Trapper-Hell 3-Dec-12 9:18am

That totally passed me - I can't get used to it yet. *Feels dumb* Sorry and thanks for all the support :)

CPallini 3-Dec-12 9:24am

You are welcome again. I felt the same the very first time I had the namespace issue.