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How to Parse Nested XML Nodes in C#

I am very new to C#, but it seems as though this should be pretty straight forward. I am trying to parse an XML string returned from a web feed that looks like this:
<autnresponse xmlns:autn="http://schemas.autonomy.com/aci/">
<action>QUERY</action>
<response>SUCCESS</response>
<responsedata>
<autn:numhits>6</autn:numhits>
<autn:hit>
<autn:reference>http://something.what.com/index.php?title=DPM</autn:reference>
<autn:id>548166</autn:id>
<autn:section>0</autn:section>
<autn:weight>87.44</autn:weight>
<autn:links>Castlmania,POUCH</autn:links>
<autn:database>Postgres</autn:database>
<autn:title>A Pouch and Mail - Castlmania</autn:title>
<autn:content>
<DOCUMENT>
<DRETITLE>Castlmania Pouch and Mail - Castlmania</DRETITLE>
<DRECONTENT>A paragraph of sorts that would contain content</DRECONTENT>
</DOCUMENT>
</autn:content>
</autn:hit>
<autn:hit>...</autn:hit>
<autn:hit>...</autn:hit>
<autn:hit>...</autn:hit>
<autn:hit>...</autn:hit>
</autnresponse>
with no luck.
I am using this code to start:
XmlDocument xmlString = new XmlDocument();
xmlString.LoadXml(xmlUrl);
XmlElement root = xmlString.DocumentElement;
XmlNode GeneralInformationNode =
root.SelectSingleNode("//autnresponse/responsedata/autn:hit");
foreach (XmlNode node in GeneralInformationNode)
{
Console.Write("reference: "+node["autn:reference"]+" Title:"+node["DRETITLE"]+"<br />);
}
And I would like to print the DRETITLE and autn:reference element of within each of the autn:hit elements. Is that even doable with my approach?
I have tried looking and several example on the good old web like this to no avail.
The error that comes back is:
System.Xml.XPath.XpathEception {NameSpace Manager or XsltContext
needed. ...}
Thanks in advance.
UPDATE:
In trying to use XmlNamespaceManager, one has to give it a url to the schema definition like so:
XmlNamespaceManager namespmng = new XmlNamespaceManager (xmlString.NameTable);
namespmng.AddNamespace("autn","http://someURL.com/XMLschema");
The problem seems to be that now the error is gone, but the data is not displaying. I should mention that I am working off of a machine that does not have internet connectivity. The other thing is the schema seems to be unavailable. I am guessing that XmlNamespaceManager would work once able to connect to the internet right?

Using System.Xml.Linq it could be something like this:
var doc = XElement.Load(xmlUrl);
var ns = doc.GetNamespaceOfPrefix("autn");
foreach (var hit in doc.Descendants(ns + "hit"))
{
var reference = hit.Element(ns + "reference").Value;
var dretitle = hit.Descendants("DRETITLE").Single().Value;
WriteLine($"ref: {reference} title: {dretitle}");
}

Firstly, the exception you're getting is because you haven't loaded the namespace using the XmlNamespaceManager for the xml you're parsing. Something like this:
XmlNamespaceManager namespaceManager = new XmlNamespaceManager(xmlString.NameTable);
if (root.Attributes["xmlns:autn"] != null)
{
uri = root.Attributes["xmlns:autn"].Value;
namespaceManager.AddNamespace("autn", uri);
}
Secondly, what you're trying to do is possible. I'd suggest using root.SelectNodes(<your xpath here>) which will return a collection of autn:hit nodes that you can loop through instead of SelectSingleNode which will return one node. Within that you can drill down to the content/DOCUMENT/DRETITLE and pull the text for the DRETITLE node using either XmlNode.Value if you select the text specifically or XmlNode.InnerText on the DRETITLE node.

XDocument get element that defines it's own namespace

As question states. I have a xml document (below) and I need to get X_ScalarWebApi_DeviceInfo that defines namespace urn:schemas-sony-com:av. Unfortunately it results in an error: {System.NullReferenceException: Object reference not set to an instance of an object. I'm mainly interested in ServiceList element, but it doesn't work as well. Platform - Windows 10 mobile.
Any ideas?
<?xml version="1.0"?>
<root xmlns="urn:schemas-upnp-org:device-1-0">
<specVersion>
<major>1</major>
<minor>0</minor>
</specVersion>
<device>
<deviceType>urn:schemas-upnp-org:device:Basic:1</deviceType>
<friendlyName>ILCE-6000</friendlyName>
<manufacturer>Sony Corporation</manufacturer>
<manufacturerURL>http://www.sony.net/</manufacturerURL>
<modelDescription>SonyDigitalMediaServer</modelDescription>
<modelName>SonyImagingDevice</modelName>
<UDN>uuid:000000001000-1010-8000-62F1894EE7BE</UDN>
<serviceList>
<service>
<serviceType>urn:schemas-sony-com:service:ScalarWebAPI:1</serviceType>
<serviceId>urn:schemas-sony-com:serviceId:ScalarWebAPI</serviceId>
<SCPDURL/>
<controlURL/>
<eventSubURL/>
</service>
</serviceList>
<av:X_ScalarWebAPI_DeviceInfo xmlns:av="urn:schemas-sony-com:av">
<av:X_ScalarWebAPI_Version>1.0</av:X_ScalarWebAPI_Version>
<av:X_ScalarWebAPI_ServiceList>
<av:X_ScalarWebAPI_Service>
<av:X_ScalarWebAPI_ServiceType>guide</av:X_ScalarWebAPI_ServiceType>
<av:X_ScalarWebAPI_ActionList_URL>http://192.168.122.1:8080/sony</av:X_ScalarWebAPI_ActionList_URL>
<av:X_ScalarWebAPI_AccessType/>
</av:X_ScalarWebAPI_Service>
<av:X_ScalarWebAPI_Service>
<av:X_ScalarWebAPI_ServiceType>accessControl</av:X_ScalarWebAPI_ServiceType>
<av:X_ScalarWebAPI_ActionList_URL>http://192.168.122.1:8080/sony</av:X_ScalarWebAPI_ActionList_URL>
<av:X_ScalarWebAPI_AccessType/>
</av:X_ScalarWebAPI_Service>
<av:X_ScalarWebAPI_Service>
<av:X_ScalarWebAPI_ServiceType>camera</av:X_ScalarWebAPI_ServiceType>
<av:X_ScalarWebAPI_ActionList_URL>http://192.168.122.1:8080/sony</av:X_ScalarWebAPI_ActionList_URL>
<av:X_ScalarWebAPI_AccessType/>
</av:X_ScalarWebAPI_Service>
</av:X_ScalarWebAPI_ServiceList>
</av:X_ScalarWebAPI_DeviceInfo>
</device>
</root>
Ah, the code:
XDocument xDoc = XDocument.Parse(xml_text);
//var av = xDoc.Root.GetDefaultNamespace();//.Attribute("xmlns");//
XNamespace av = "urn:schemas-sony-com:av";
System.Diagnostics.Debug.WriteLine(av);
<XElement> api_list = (List<XElement>)xDoc.Element(av + "X_ScalarWebAPI_DeviceInfo").Elements();
==EDIT==
Well, both solutions were ok, so I'm upvoting one and marking as answer the other :P
It was mentioned that the solution using only a 'local name' might cause false positive search results, so to be safe I'm using the first one. Thanks for help!

Element only returns elements directly beneath the current node. You need the to specify the entire path (note there are multiple namespaces):
XNamespace ns = "urn:schemas-upnp-org:device-1-0";
XNamespace av = "urn:schemas-sony-com:av";
var api_list = xDoc.Root.Element(ns + "device")
.Element(av + "X_ScalarWebAPI_DeviceInfo").Elements();

Using Xml Linq
XDocument doc = XDocument.Load(FILENAME);
XElement x_ScalarWebAPI_DeviceInfo = doc.Descendants().Where(x => x.Name.LocalName == "X_ScalarWebAPI_DeviceInfo").FirstOrDefault();
XNamespace ns = x_ScalarWebAPI_DeviceInfo.Name.Namespace;

The issue is indeed the Element or Elements methods only search the direct child elements. You can use Decendants() but you will get a collection, so you have to do First(expression) to het a single one.
But in the expression you can use .Name.LocalName to skip the whole namespace thing and look for just the name of the element.
For this question:
XDocument xDoc = XDocument.Parse(xml_text);
XElement x_ScalarWebAPI_DeviceInfo = doc.Descendants().First(x.Name.LocalName == "X_ScalarWebAPI_DeviceInfo");

Issues Querying XML with Namespace

I am attempting to consume a Rest service that returns an XML response. I have successfully made the get request, my problem is processing the response. The response includes a namespace that seems to be messing up my linq query. I have tried almost everything I can think of userNames always comes up empty. Any help would be greatly appreciated and could possibly save my sanity.
<?xml version="1.0" encoding="UTF-8"?>
<tsResponse xmlns="http://tableausoftware.com/api" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://tableausoftware.com/api http://tableausoftware.com/api/ts-api-2.0.xsd">
<users>
<user id="c9274ce9-0daa-4aad-9bd2-3b1d6d402119" name="_DevITTemplate" role="Unlicensed" publish="false" contentAdmin="false" lastLogin="" externalAuthUserId=""/>
string usersList =
request.DownloadString("http://bshagena-sandbox/api/2.0/sites/b4126fe9-d7ee-4083-88f9- a5eea1f40416/users/");
request.Dispose();
XDocument xd;
XElement users;
XNamespace ns = "http://tableausoftware.com/api";
xd = XDocument.Parse(usersList);
users = xd.Root.Elements().First();
var userNames = from a in users.Descendants(ns +"users")
select (string)a.Attribute("name").Value;

It is your user element which contains attribute name, not the names wrapper element. Adjust your xpath accordingly: (Your use of the XNamespace is fine)
var userNames = from a in users.Descendants(ns + "user")
select a.Attribute("name").Value;
Minor - Attribute.Value is already a string - no need to cast it :)

Here is what I did and it seemed to work. Sorry for all the comments. I am sure this is not the most efficient way to do this. I hope this helps someone else losing their mind over the same issue.
// Sends get request and stores response as a string
string usersList =
request.DownloadString("http://<serverName>/api/2.0/sites/b4126fe9-d7ee-4083-88f9-a5eea1f40416/users/");
// declares an XML document object
XDocument xd;
// Declares and XML element object
XElement users;
// Declares a stupid XML namespace object
XNamespace ns = "http://tableausoftware.com/api";
// Sets document to value of string
xd = XDocument.Parse(usersList);
// Sets the element to value of the first node of the xml document
users = xd.Root.Elements().First();
// Creates an array and queries elements based on attribute of name
var userNames = from a in users.Elements(ns + "user")
select (string)a.Attribute("name").Value;

XElement descendant not working \ XElement.Parse() [duplicate]

I'm a completly New to Linq2XML as I code to much lines to perform simple things, and in a simple project I wanted to give it a try...
I'm with this for 2 hours and nothing I do get's it right :(
I'm really, really thinking to go back to XmlNode-code-alike
The Task:
I send a SOAP Action to an ASMX service and I get the response as XML
I Parse the XML into a XDocument object
I try to get a list of nodes ... err! Problem!
as you can see from this screenshot
alt text http://www.balexandre.com/temp/2010-02-26_0038.png
my XDocument has a Node called TransactionInformationType witch is a Sequence, and I simple want to get all and retrieve the only 2 variables that I need (you can see the code commented) just below select c;
in the Watch window you can see that
doc.Descendants("TransactionInformationType")
returns nothing at all, and seeing by the content of the XDocument in the Text Visualizer, it does exist!
Anyone care to explain and help me passing this HUGE wall?
Thank you!
Added
XDocument content
Answer
the Response XML has
<gettransactionlistResponse xmlns="https://ssl.ditonlinebetalingssystem.dk/remote/payment">
and I must use this as Namespace!
turns out that, to retrieve values, I do need to use the XNamespace as well, so the final code looks like this:
// Parse XML
XDocument doc = XDocument.Parse(strResponse);
XNamespace ns = "https://ssl.ditonlinebetalingssystem.dk/remote/payment";
var trans = from item in doc.Descendants(ns + "TransactionInformationType")
select new TransactionInformationType
{
capturedamount = Convert.ToInt32(item.Element(ns + "capturedamount").Value),
orderid = item.Element(ns + "cardtypeid").Value
};
Thank you all for the help!

var result = doc.Descendants("TransactionInformationType");
selects all descendants in the XDocument that have element name "TransactionInformationType" and are in the empty namespace.
From you screenshot it seems the element you're trying to select is in the namespace "https://ssl.ditonlinebetalingssystem.dk/remote/payment" though.
You need to specify that explicitly:
XNamespace ns = "https://ssl.ditonlinebetalingssystem.dk/remote/payment";
↑↑ ↑
var result = doc.Descendants(ns + "TransactionInformationType");

This should solve you isssue (replace the namespace with the right URL):
XNamespace ns = "https://ssl.ditonline...";
doc.Descendants(ns + "TransactionInformationType");

Using LINQ to XML to Process XML in Multiple Namespaces

I'm trying to parse results from the YouTube API. I'm getting the results correctly as a string, but am unable to parse it correctly.
I followed suggestions on a previous thread, but am not getting any results.
My sample code is:
string response = youtubeService.GetSearchResults(search.Term, "published", 1, 50);
XDocument xDoc = XDocument.Parse(response, LoadOptions.SetLineInfo);
var list = xDoc.Descendants("entry").ToList();
var entries = from entry in xDoc.Descendants("entry")
select new
{
Id = entry.Element("id").Value,
Categories = entry.Elements("category").Select(c => c.Value)
//Published = entry.Element("published").Value,
//Title = entry.Element("title").Value,
//AuthorName = entry.Element("author").Element("name").Value,
//Thumnail = entry.Element("media:group").Elements("media:thumnail").ToList().ElementAt(0)
};
foreach (var entry in entries)
{
// entry.Id and entry.Categories available here
}
The problem is that entries has a count of 0 even though the XDocument clearly has the valid values.
The value of the response variable (Sample XML) can be seen here: http://snipt.org/lWm
(FYI: The youTube schema is listed here: http://code.google.com/apis/youtube/2.0/developers_guide_protocol_understanding_video_feeds.html)
Can anyone tell me what I'm doing wrong here?

All the data is in the "http://www.w3.org/2005/Atom" namespace; you need to use this throughout:
XNamespace ns = XNamespace.Get("http://www.w3.org/2005/Atom");
...
from entry in xDoc.Descendants(ns + "entry")
select new
{
Id = entry.Element(ns + "id").Value,
Categories = entry.Elements(ns + "category").Select(c => c.Value)
...
};
etc (untested)

When you see prefix:name, it means that name is in the namespace whose prefix has been declared as prefix. If you look at the top of the document, you'll see an xmlns:media=something. The something is the namespace used for anything with the prefix media.
This means you need to create an XNamespace for each of the namespaces you need to reference:
XNamespace media = XNamespace.Get("http://search.yahoo.com/mrss/");
and then use media for the names in that namespace:
media + "group"
The namespaces in this document are:
xmlns="http://www.w3.org/2005/Atom"
xmlns:app="http://www.w3.org/2007/app"
xmlns:media="http://search.yahoo.com/mrss/"
xmlns:openSearch="http://a9.com/-/spec/opensearch/1.1/"
xmlns:gd="http://schemas.google.com/g/2005"
xmlns:gml="http://www.opengis.net/gml"
xmlns:yt="http://gdata.youtube.com/schemas/2007"
xmlns:georss="http://www.georss.org/georss"

You need to set the namespace.
Creating an XName in a Namespace
As with XML, an XName can be in a namespace, or it can be in no namespace.
For C#, the recommended approach for creating an XName in a namespace is to declare the XNamespace object, then use the override of the addition operator.
http://msdn.microsoft.com/en-us/library/system.xml.linq.xname.aspx