I'm playing around a bit with XPath and nodelist and i want to extract
some info from a RSS feed.
The one that i am testing at can be viewed at http://slashdot.org/index.rss
Ok.. heres the deal:
I load xml via httpwebrequest etc and put it in a XmlDocument.
xmlFeed.Load(xR es.GetResponseS tream());
This works fine as i can use this stream with a XmlReader to parse the
document in an ugly way.
Now i try to get all the title elemelts:
nodeList = xmlFeed.Documen tElement.Select Nodes("RDF/item/title/text()");
This should (according to my browsing of xpath and thing and reading for
a few hrs) result in getting the titles ;)
But it don't.
System.Console. WriteLine("Node s: " + nodeList.Count + "\n");
Outputs: "Nodes: 0"
So what part of my brain isnt working? :)
Anyone spot something horribly wrong?
---
Øyvind Jægtnes 8 4241
I'm no expert on xpath, but I think you need:
nodeList = xmlFeed.Documen tElement.Select Nodes("/RDF/item/title/text()");
The RDF node must be prefixed with a forward slash to show it is an absolute
path from the root of the document...
Try it and see?
"Øyvind Jægtnes" <oj****@start.n o> wrote in message
news:0z******** ************@ne ws4.e.nsc.no... I'm playing around a bit with XPath and nodelist and i want to extract some info from a RSS feed. The one that i am testing at can be viewed at
http://slashdot.org/index.rss Ok.. heres the deal: I load xml via httpwebrequest etc and put it in a XmlDocument.
xmlFeed.Load(xR es.GetResponseS tream());
This works fine as i can use this stream with a XmlReader to parse the document in an ugly way.
Now i try to get all the title elemelts:
nodeList = xmlFeed.Documen tElement.Select Nodes("RDF/item/title/text()");
This should (according to my browsing of xpath and thing and reading for a few hrs) result in getting the titles ;) But it don't. System.Console. WriteLine("Node s: " + nodeList.Count + "\n"); Outputs: "Nodes: 0"
So what part of my brain isnt working? :) Anyone spot something horribly wrong?
--- Øyvind Jægtnes
Iain A. Mcleod wrote: I'm no expert on xpath, but I think you need: nodeList = xmlFeed.Documen tElement.Select Nodes("/RDF/item/title/text()");
The RDF node must be prefixed with a forward slash to show it is an absolute path from the root of the document...
Try it and see?
Still same.
But when i debug and look at the XmlElement of <rdf:RDF> it sais:
LocalName is RDF and Name is rdf:RDF.
I then made this XPath string: "/rdf:RDF/item/title/text()"
it trows exception on that :p
System.Xml.XPat h.XPathExceptio n: Namespace Manager or XsltContext
needed. This query has a prefix, variable, or user-defined function.
Which i cant really decode ;)
Do i need to use Namespace Manager to get a proper query?
---
Øyvind Jægtnes
Øyvind Jægtnes wrote: Iain A. Mcleod wrote:
I'm no expert on xpath, but I think you need: nodeList = xmlFeed.Documen tElement.Select Nodes("/RDF/item/title/text()");
The RDF node must be prefixed with a forward slash to show it is an absolute path from the root of the document...
Try it and see?
Still same. But when i debug and look at the XmlElement of <rdf:RDF> it sais: LocalName is RDF and Name is rdf:RDF.
I then made this XPath string: "/rdf:RDF/item/title/text()"
it trows exception on that :p
Actually i've been poking around a bit and i think it has to do with
rdf:RDF is its name, but SelectNodes think that it is a prefix for a
namespace when i use it. Question then is, is it posible to "escape" the
: in someway in the query?
---
Øyvind Jægtnes
Sorry man, way over my head!
Hope someone else can help you :)
"Øyvind Jægtnes" <oj****@start.n o> wrote in message
news:H3******** ************@ne ws2.e.nsc.no... Øyvind Jægtnes wrote: Iain A. Mcleod wrote:
I'm no expert on xpath, but I think you need: nodeList =
xmlFeed.Documen tElement.Select Nodes("/RDF/item/title/text()"); The RDF node must be prefixed with a forward slash to show it is an absolute path from the root of the document...
Try it and see?
Still same. But when i debug and look at the XmlElement of <rdf:RDF> it sais: LocalName is RDF and Name is rdf:RDF.
I then made this XPath string: "/rdf:RDF/item/title/text()"
it trows exception on that :p
Actually i've been poking around a bit and i think it has to do with rdf:RDF is its name, but SelectNodes think that it is a prefix for a namespace when i use it. Question then is, is it posible to "escape" the : in someway in the query?
--- Øyvind Jægtnes
Øyvind Jægtnes wrote: I'm playing around a bit with XPath and nodelist and i want to extract some info from a RSS feed. The one that i am testing at can be viewed at http://slashdot.org/index.rss
Ok.. heres the deal: I load xml via httpwebrequest etc and put it in a XmlDocument.
xmlFeed.Load(xR es.GetResponseS tream());
This works fine as i can use this stream with a XmlReader to parse the document in an ugly way.
Now i try to get all the title elemelts:
nodeList = xmlFeed.Documen tElement.Select Nodes("RDF/item/title/text()");
This should (according to my browsing of xpath and thing and reading for a few hrs) result in getting the titles ;)
Nope, you forgot about namespaces. It should be something like
XmlNamespaceMan ager nm = new XmlNamespaceMan ager(xmlFeed.Na meTable);
nm.AddNamespace ("rdf", "http://www.w3.org/1999/02/22-rdf-syntax-ns#");
nm.AddNamespace ("rss", "http://purl.org/rss/1.0/");
nodeList =
xmlFeed.Documen tElement.Select Nodes("rdf:RDF//rss:item/title/text()");
Read "XML Namespaces and How They Affect XPath and XSLT" at http://msdn.microsoft.com/library/en...ml05202002.asp
--
Oleg Tkachenko [XML MVP] http://blog.tkachenko.com
Oleg Tkachenko [MVP] wrote: Øyvind Jægtnes wrote:
Now i try to get all the title elemelts:
nodeList = xmlFeed.Documen tElement.Select Nodes("RDF/item/title/text()");
Nope, you forgot about namespaces. It should be something like
XmlNamespaceMan ager nm = new XmlNamespaceMan ager(xmlFeed.Na meTable); nm.AddNamespace ("rdf", "http://www.w3.org/1999/02/22-rdf-syntax-ns#"); nm.AddNamespace ("rss", "http://purl.org/rss/1.0/"); nodeList = xmlFeed.Documen tElement.Select Nodes("rdf:RDF//rss:item/title/text()");
Hmm this actually throws exception ;)
But with:
nodeList =
xmlFeed.Documen tElement.Select Nodes("/rdf:RDF//rss:item/title/text()", nm);
nodeList.Count is still 0.
When i use "//*" as XPath line it takes the whole document as it should.
But if i do "/*/*/title/text()", or "//*//*/title" or any variations of
that i still get 0 count...
So im really confused ;)
Starting to wander if the best way to use XML is to iterate the nodes
and do the searching manually.. but XPath looks cool if it would work :p
Read "XML Namespaces and How They Affect XPath and XSLT" at http://msdn.microsoft.com/library/en...ml05202002.asp
Will do..
---
Øyvind Jægtnes
Oleg Tkachenko [MVP] wrote: Read "XML Namespaces and How They Affect XPath and XSLT" at http://msdn.microsoft.com/library/en...ml05202002.asp
Ok, solved ;)
I finally got them extrated.. Now its time to see if i can actually use
the namespaces to check the document version (rss 0.9, 1.0, 2.0). That
would be nice :)
(correct xpath was "/rdf:RDF//rss:item/rss:title/text()")
---
Øyvind Jægtnes wrote: I'm playing around a bit with XPath and nodelist and i want to extract some info from a RSS feed. The one that i am testing at can be viewed at http://slashdot.org/index.rss
Ah finally i have something semi working here ;)
While project can be seen at http://home.no.net/~ojaegt/Rss.rar if
someone are interested.
Still todo: make it so you can save a list of feeds and select between
them (GUI) and add support for ATOM feeds (library).
---
Øyvind Jægtnes This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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