reading node from xml file in XMLDocument

Question

i am trying to grab the TopicName how should i go after it and try different combination but somehow i am unable to get TopicName below is my source codee...

XmlDocument xdoc = new XmlDocument();//xml doc used for xml parsing xdoc.Load( "http://latestpackagingnews.blogspot.com/feeds/posts/default" );//loading XML in xml doc XmlNodeList xNodelst = xdoc.DocumentElement.SelectNodes("content");//reading node so that we can traverse thorugh the XML foreach (XmlNode xNode in xNodelst)//traversing XML { //litFeed.Text += "read"; }

sample xml file

<content type="application/xml"> <CatalogItems xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="sitename.xsd"> <CatalogSource Acronym="ABC" OrganizationName="ABC Corporation" /> <CatalogItem Id="3212" CatalogUrl="urlname"> <ContentItem xmlns:content="sitename.xsd" TargetUrl="url"> <content:SelectionSpec ClassList="" ElementList="" /> <content:Language Value="eng" Scheme="ISO 639-2" /> <content:Source Acronym="ABC" OrganizationName="ABC Corporation" /> <content:Topics Scheme="ABC"> <content:Topic TopicName="Marketing" /> <content:Topic TopiccName="Coverage" /> </content:Topics> </ContentItem> </CatalogItem> </CatalogItems> </content>

The Url in your newly updated sample code produces totally different Xml than your sample xml, there is not CatalogItem nor content namespace in that xml. — BrokenGlass
– BrokenGlass, Commented Sep 17, 2011 at 4:22

BrokenGlass · Accepted Answer · 2011-09-17 01:12:00Z

The Topic nodes in your XML are using the content namespace - you need to declare and use the XML namespace in your code, then you can use SelectNodes() to grab the nodes of interest - this worked for me:

XmlNamespaceManager nsmgr = new XmlNamespaceManager(xdoc.NameTable); nsmgr.AddNamespace("content", "sitename.xsd"); var topicNodes = xdoc.SelectNodes("//content:Topic", nsmgr); foreach (XmlNode node in topicNodes) { string topic = node.Attributes["TopicName"].Value; }

Just as a comparison see how easy this would be with Linq to XML:

XDocument xdoc = XDocument.Load("test.xml"); XNamespace ns = "sitename.xsd"; string topic = xdoc.Descendants(ns + "Topic") .Select(x => (string)x.Attribute("TopicName")) .FirstOrDefault();

To get all topics you can replace the last statement with:

var topics = xdoc.Descendants(ns + "Topic") .Select(x => (string)x.Attribute("TopicName")) .ToList();

if i use #1 solution i get this error Namespace prefix content is not defined
@Abu: I tested this and code works fine for me - did you include the namespace manager?
Also this assumes you have already loaded your xml into xdoc
if i use the second option which is linq to xml i will get just one topicname based on your code but where as i will have mulitple topicname as you loop through all my xml... just wondering how would you do that
@Abu: Your xml currently has only one topic name - I guess TopiccName in the second node is a typo then? - Answer updated

AaronLS · Accepted Answer · 2011-09-16 21:59:49Z

If you just need a specific element, then I'd use XPath:

This is a guide to use XPath in C#: http://www.codeproject.com/KB/XML/usingXPathNavigator.aspx

And this is the query that will get you a collection of your Topics:

//content/CatalogItems/CatalogItem/ContentItem/content:Topics/content:Topic

You could tweak this query depending on what it is you're trying to accomplish, grabbing just a specific TopicName value:

//content/CatalogItems/CatalogItem/ContentItem/content:Topics/content:Topic/@TopicName

XPath is pretty easy to learn. I've done stuff like this pretty quickly with no prior knowledge.

You can paste you XML and xpath query here to test your queries:

http://www.bit-101.com/xpath/

i tried the first solution but did not work... it retuns 0 count.
If you copy your XML and that query in the xpath tool you see it should be returning an item so not sure what is going wrong.
will you show me the steps i tried pasting the xml in the www.bit-101.com/xpath tool and after that? on the right side it says undefined

SoManyGoblins · Accepted Answer · 2011-09-16 23:00:19Z

The following quick and dirty LINQ to XML code obtains your TopicNames and prints them on the console.

XDocument lDoc = XDocument.Load(lXmlDocUri); foreach (var lElement in lDoc.Element("content").Element(XName.Get("CatalogItems", "sitename.xsd")).Elements(XName.Get("CatalogItem", "sitename.xsd"))) { foreach (var lContentTopic in lElement.Element(XName.Get("ContentItem", "sitename.xsd")).Element(XName.Get("Topics", "sitename.xsd")).Elements(XName.Get("Topic", "sitename.xsd"))) { string lTitle = lContentTopic.Attribute("TopicName").Value; Console.WriteLine(lTitle); } }

It'd have been a lot shorter if it wasn't for all the namespaces :) (Instead of "XName.Get" you would just use the name of the element).

throwing an error first foreach the errors is object reference not set to an instance of an object
My code works for your sample, for generic XMLs in which there might not be a content node, for example, you just need to ask if lDoc.Element("content") != null.

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