Develop Reference

Accessing a sub attribute in a XML file using XElement

In C#, I am trying to change an option of a feature in an XML file which presents a Print Ticket and loaded as an XElement by the following code:
XElement ticketRootXElement = null;
using (Stream ticketReadStream = displayedPrintTicket.GetReadStream())
{
ticketRootXElement = XElement.Load(ticketReadStream);
}
The partial XML is something like following:
<?xml version="1.0"?>
<psf:Feature xmlns:psf="http://schemas.microsoft.com/windows/2003/08/printing/printschemaframework" name="psk:PageMediaSize">
<psf:Option name="psk:ISOA4">
<psf:ScoredProperty name="psk:MediaSizeWidth">
<psf:Value xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="xsd:integer">210000</psf:Value>
</psf:ScoredProperty>
<psf:ScoredProperty name="psk:MediaSizeHeight">
<psf:Value xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="xsd:integer">297000</psf:Value>
</psf:ScoredProperty>
</psf:Option>
</psf:Feature>
How can I access the "Option" of a specific "Feature" and change it to something like <psf:Option name="psk:ISOA3">?
I tried the following code, but it fails.
foreach (XAttribute xAttr in ticketRootXElement.Descendants(xns_psf + "Feature").Attributes())
{
if (xAttr.Value.Equals("psk:PageMediaSize"))
{
foreach(XAttribute xSubAttr in ticketRootXElement.Element("PageMediaSize").Descendants(xns_psf + "Option").Attributes())
{
if (xAttr.NextAttribute.Name.LocalName.Equals("name"))
{
xAttr.NextAttribute.SetValue("psk:ISO" + cmb_PaperSize.SelectedValue.ToString());
}
}
}
}

You can can modify the option value of your selected feature as as follows:
var featureName = "psk:PageMediaSize";
var newOptionValue = "psk:ISOA3"; // Your modified value here
XNamespace xns_psf = #"http://schemas.microsoft.com/windows/2003/08/printing/printschemaframework";
var query = from f in ticketRootXElement.DescendantsAndSelf(xns_psf + "Feature")
where (string)f.Attribute("name") == featureName
select f;
foreach (var f in query)
{
// TODO: handle the situation were a child <psf:Option> element is missing.
f.Element(xns_psf + "Option").SetAttributeValue("name", newOptionValue);
}
Notes:
XElement.Attribute(XName) can be used to look up an attribute by name, and XElement.SetAttributeValue(XName, Object) can be used to set or add an attribute value by name.
Casting an XAttribute to a string returns the value of the attribute, or null if the attribute was missing, and so is convenient to use when filtering by attribute value in a where statement.
If the selected <psf:Feature> element does not have a child <psf:Option> element, the above code will throw an exception. You will need to check your XML schema to determine whether this is possible, and if so, how to handle it.
Demo fiddle here.

Actually I did it using the following code. But "bdc" solution (above answer) sounds much better:
var element = ticketRootXElement.Descendants(xns_psf + "Feature")
.Where(arg => arg.Attribute("name").Value == "psk:PageMediaSize")
.Single();
var subelement = element.Descendants(xns_psf + "Option")
.Single();
subelement.FirstAttribute.SetValue("psk:ISOA3");

How add,edit and delete node by line in xml

I have string XML. I loaded to XmlDocument. How can I add, edit and delete by simplest method by line, because I know only line which I should edit. It's better work wih XML like with string, or better work with XmlDocuments?
using System;
using System.Xml;
namespace testXMl
{
class Program
{
static void Main(string[] args)
{
string xml="<?xml version=\"1.0\"?>\r\n<application>\r\n<features>\r\n<test key=\"some_key\">\r\n</features>\r\n</application>";
XmlDocument xm = new XmlDocument();
xm.LoadXml(xml);
//Edit third line
//xm[3].EditName(featuresNew);
//xml->"<?xml version=\"1.0\"?>\r\n<application>\r\n<featuresNew>\r\n<test key=\"some_key\">\r\n</featuresNew>\r\n</application>"
//Add fourth line the Node
//xm[4].AddNode("FeatureNext");
//xml->"<?xml version=\"1.0\"?>\r\n<application>\r\n<FeatureNext>\r\n<FeatureNext>\r\n</features2>\r\n<test key=\"some_key\">\r\n</features>\r\n</application>"
//Delete sixth line
//xm[6].DeleteNode;
//xml->"<?xml version=\"1.0\"?>\r\n<application>\r\n<FeatureNext>\r\n<FeatureNext>\r\n</features2>\r\n</features>\r\n</application>"
}
}
}
Thanks, in advance.

You should always work with XDocument/XmlDocument objects. A key knowledge is the XPath query language.
This a quick XML crash course. Run with debugger and inspect the XML variable as you move on.
var xml = new XmlDocument();
xml.LoadXml(#"<?xml version='1.0'?>
<application>
<features>
<test key='some_key' />
</features>
</application>");
// Select an element to work with; I prefer to work with XmlElement instead of XmlNode
var test = (XmlElement) xml.SelectSingleNode("//test");
test.InnerText = "another";
test.SetAttribute("sample", "value");
var attr = test.GetAttribute("xyz"); // Works, even if that attribute doesn't exists
// Create a new element: you'll need to point where you should add a child element
var newElement = xml.CreateElement("newElement");
xml.SelectSingleNode("/application/features").AppendChild(newElement);
// You can also select elements by its position;
// in this example, take the second element inside "features" regardless its name
var delete = xml.SelectSingleNode("/application/features/*[2]");
// Trick part: if you found the element, navigate to its parent and remove the child
if (delete != null)
delete.ParentNode.RemoveChild(delete);

Updating a specific XML node

I am new to XML files and how to manage them. This is for a web app I am writing (aspx).
At the present time I am able to find the first instance of a node and add an item to it with the following code:
xmlClone.Element("PCs").Element("PC").Element("pc_hwStatus").AddAfterSelf(new XElement("user_name", txt_v0_nombre.Text));
What I really want is to add ("user_name", txt_v0_nombre.Text) to a node in particular, not the first one. The content of my XML file is:
<PCs>
<PC>
<pc_name>esc01</pc_name>
<pc_ip>10.10.10.10</pc_ip>
<pc_hwStatus>Working</pc_hwStatus>
</PC>
<PC>
<pc_name>esc02</pc_name>
<pc_ip>10.10.10.11</pc_ip>
<pc_hwStatus>Under Maintenance</pc_hwStatus>
</PC>
</PCs>
The decision of what node to update is made selecting an item from a dropdown list (the PC name).
With my current code, the new item is always added as last line of node with "pc_
name = esc01". I want to be able to added it to esc02 or esc03 and so on... How can this be accomplished? (Using xdocument)

If I understand you correctly, what you are looking for is the FirstOrDefault extension method. In there specify which node you are wanting, in this case a string from your dropdown box, which can be passed in. So to get the first node:
var pc = xmlClone.Element("PCs").Elements("PC").FirstOrDefault(e => e.Element("pc_name").Value == "esc01");
Now you have this in your XElement:
<PC>
<pc_name>esc01</pc_name>
<pc_ip>10.10.10.10</pc_ip>
<pc_hwStatus>Working</pc_hwStatus>
</PC>
To get any element like that, just replace this clause:
.FirstOrDefault(e => e.Element("pc_name").Value == "esc01");
with this one
.FirstOrDefault(e => e.Element("pc_name").Value == desiredPC);
where desiredPC is the value of the xml node: pc_name.
Now to add your data just call the plain old Add method:
pc.Add(new XElement("user_name", txt_v0_nombre.Text);
That should do the trick for you.

Here's a solution that uses LINQ query syntax with LINQ to XML:
XDocument document = XDocument.Parse(xmlContent);
string pcName = "esc02";
IEnumerable<XElement> query =
from pc in document.Element("PCs").Elements("PC")
where pc.Element("pc_name").Value.Equals(pcName)
select pc;
XElement xe = query.FirstOrDefault();
if (xe != null)
{
xe.Add(new XElement("user_name", "DMS"));
}
I have incorporated your sample data and this query into a demonstration program. Please see below for the output from the demonstration program followed by the program itself.
Expected Output
<PC>
<pc_name>esc02</pc_name>
<pc_ip>10.10.10.11</pc_ip>
<pc_hwStatus>Under Maintenance</pc_hwStatus>
<user_name>DMS</user_name>
</PC>
Demonstration Program
using System;
using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;
namespace LinqToXmlDemo
{
public class Program
{
public static void Main(string[] args)
{
string xmlContent = GetXml();
XDocument document = XDocument.Parse(xmlContent);
XElement xe = FindPCName(document, "esc02");
if (xe != null)
{
xe.Add(new XElement("user_name", "DMS"));
Console.WriteLine(xe);
}
else
{
Console.WriteLine("Query returned no results.");
}
}
private static XElement FindPCName(XDocument document, String pcName)
{
IEnumerable<XElement> query =
from pc in document.Element("PCs").Elements("PC")
where pc.Element("pc_name").Value.Equals(pcName)
select pc;
return query.FirstOrDefault();
}
private static String GetXml()
{
return
#"<?xml version='1.0' encoding='utf-8'?>
<PCs>
<PC>
<pc_name>esc01</pc_name>
<pc_ip>10.10.10.10</pc_ip>
<pc_hwStatus>Working</pc_hwStatus>
</PC>
<PC>
<pc_name>esc02</pc_name>
<pc_ip>10.10.10.11</pc_ip>
<pc_hwStatus>Under Maintenance</pc_hwStatus>
</PC>
</PCs>";
}
}
}

Method .Element returns the first element with the specified name.
You can get the whole list with method .Elements, and iterate this list to find the one you are looking for.

XPathSelectElements returns null

Load function is already defined in xmlData class
public class XmlData
{
public void Load(XElement xDoc)
{
var id = xDoc.XPathSelectElements("//ID");
var listIds = xDoc.XPathSelectElements("/Lists//List/ListIDS/ListIDS");
}
}
I'm just calling the Load function from my end.
XmlData aXmlData = new XmlData();
string input, stringXML = "";
TextReader aTextReader = new StreamReader("D:\\test.xml");
while ((input = aTextReader.ReadLine()) != null)
{
stringXML += input;
}
XElement Content = XElement.Parse(stringXML);
aXmlData.Load(Content);
in load function,im getting both id and and listIds as null.
My test.xml contains
<SEARCH>
<ID>11242</ID>
<Lists>
<List CURRENT="true" AGGREGATEDCHANGED="false">
<ListIDS>
<ListID>100567</ListID>
<ListID>100564</ListID>
<ListID>100025</ListID>
<ListID>2</ListID>
<ListID>1</ListID>
</ListIDS>
</List>
</Lists>
</SEARCH>

EDIT: Your sample XML doesn't have an id element in the namespace with the nss alias. It would be <nss:id> in that case, or there'd be a default namespace set up. I've assumed for this answer that in reality the element you're looking for is in the namespace.
Your query is trying to find an element called id at the root level. To find all id elements, you need:
var tempId = xDoc.XPathSelectElements("//nss:id", ns);
... although personally I'd use:
XDocument doc = XDocument.Parse(...);
XNamespace nss = "http://schemas.microsoft.com/SQLServer/reporting/reportdesigner";
// Or use FirstOrDefault(), or whatever...
XElement idElement = doc.Descendants(nss + "id").Single();
(I prefer using the query methods on LINQ to XML types instead of XPath... I find it easier to avoid silly syntax errors etc.)
Your sample code is also unclear as you're using xDoc which hasn't been declared... it helps to write complete examples, ideally including everything required to compile and run as a console app.

I am looking at the question 3 hours after it was submitted and 41 minutes after it was (last) edited.
There are no namespaces defined in the provided XML document.
var listIds = xDoc.XPathSelectElements("/Lists//List/ListIDS/ListIDS");
This XPath expression obviously doesn't select any node from the provided XML document, because the XML document doesn't have a top element named Lists (the name of the actual top element is SEARCH)
var id = xDoc.XPathSelectElements("//ID");
in load function,im getting both id and and listIds as null.
This statement is false, because //ID selects the only element named ID in the provided XML document, thus the value of the C# variable id is non-null. Probably you didn't test thoroughly after editing the XML document.
Most probably the original ID element belonged to some namespace. But now it is in "no namespace" and the XPath expression above does select it.

string xmldocument = "<response xmlns:nss=\"http://schemas.microsoft.com/SQLServer/reporting/reportdesigner\"><action>test</action><id>1</id></response>";
XElement Content = XElement.Parse(xmldocument);
XPathNavigator navigator = Content.CreateNavigator();
XmlNamespaceManager ns = new XmlNamespaceManager(navigator.NameTable);
ns.AddNamespace("nss", "http://schemas.microsoft.com/SQLServer/reporting/reportdesigner");
var tempId = navigator.SelectSingleNode("/id");

The reason for the null value or system returned value is due to the following
var id = xDoc.XPathSelectElements("//ID");
XpathSElectElements is System.xml.linq.XElment which is linq queried date. It cannot be directly outputed as such.
To Get individual first match element
use XPathSelectElement("//ID");
You can check the number of occurrences using XPathSelectElements as
var count=xDoc.XPathSelectElements("//ID").count();
you can also query the linq statement as order by using specific conditions
Inorder to get node value from a list u can use this
foreach (XmlNode xNode in xDoc.SelectNodes("//ListIDS/ListID"))
{
Console.WriteLine(xNode.InnerText);
}
For Second list you havnt got the value since, the XPath for list items is not correct

Change Value of the last Attribute in an XML c#

I was working on a bunch of XMLs that all share an attribute that contains the string "name" in them. The following code selects the attribute with string "name" in it and assign a new value to it.
public void updateXmlFile(string strFileName)
{
try
{
//Load the Document
XmlDocument doc = new XmlDocument();
doc.Load(strFileName);
//Set the changed Value
string newValue = GetUniqueKey();
//Select all nodes in the XML then choose from them
//the first node that contain string "name" in it
XmlNodeList list = doc.SelectNodes("//#*");
XmlNode filteredNode = list.Cast<XmlNode>()
.First(item => item.Name.ToLower().Contains("name"));
//Assign the newValue to the value of the node
filteredNode.Value = newValue;
doc.Save(strFileName);
}
catch (XmlException xex) { Console.WriteLine(xex); }
}
Now a new XMLs were added that dosen't have the string "name" in them, so instead of modifying the attribute with string "name" in it I decided to simply modify the last attribute no matter what it was (not the first)
Can anybody tell me how to do that?
EDIT
Here is an example of my XML
<?xml version="1.0" encoding="utf-8"?>
<CO_CallSignLists Version="24" ModDttm="2010-09-13T06:45:38.873" ModUser="EUADEV\SARE100" ModuleOwner="EUADEVS06\SS2008" CreateDttm="2009-11-05T10:19:31.583" CreateUser="EUADEV\A003893">
<CoCallSignLists DataclassId="E3FC5E2D-FE84-492D-AD94-3ACCED870714" EntityId="E3FC5E2D-FE84-492D-AD94-3ACCED870714" MissionID="4CF71AB2-0D92-DE11-B5D1-000C46F3773D" BroadcastType="S" DeputyInSpecialList="1" SunSpots="1537634cb70c6d80">
<CoCallSigns EntityId="DEBF1DDB-3C92-DE11-A280-000C46F377C4" CmdID="C45F3EF1-1292-DE11-B5D1-000C46F3773D" ModuleID="6CB497F3-AD63-43F1-ACAE-2C5C3B1D7F61" ListType="HS" Name="Reda Sabassi" Broadcast="INTO" PhysicalAddress="37" IsGS="1" HCId="0" CommonGeoPos="1" GeoLat="0.0000000" GeoLong="0.0000000">
<CoRadios EntityId="E1BF1DDB-3C92-DE11-A280-000C46F377C4" RadioType="HF" />
</CoCallSigns>
</CoCallSignLists>
</CO_CallSignLists>
#Alex: You notice that the "SunSpots" attribute (last attribute in the first child element) is successfully changed. But now when I wanna load the XML back into the DB it gives me an error
Here is the modified code
public void updateXmlFile(string strFileName)
{
try
{
XDocument doc = XDocument.Load(strFileName);
XAttribute l_attr_1 = (doc.Elements().First().Elements().First().Attributes().Last());
l_attr_1.Value = GetUniqueKey();
Console.WriteLine("Name: {0} Value:{1}", l_attr_1.Name, l_attr_1.Value);
doc.Save(strFileName);
}
catch (XmlException xex) { Console.WriteLine(xex); }
}
I was thinking of making an if statment which checks if the XML has an attribute that contains string "name" in it (since most of my XMLs has an attribute that contains name in them) if it does then change the attribute's value if not look for the last attribute and change it.. not the best solution but just throwing it out there

Then definitely use Linq to XML.
Example:
using System.Xml.Linq;
string xml = #"<?xml version=""1.0"" encoding=""utf-8""?>
<Commands Version=""439"" CreateUser=""Reda"">
<CmCommands DataclassId=""57067ca8-ef96-4d2e-a085-6bd7e8b24126"" OrderName = ""Tea"" Remark=""Black"">
<CmExecutions EntityId=""A9A5B0F2-6AB4-4619-9106-B0F85F86EE01"" Lock=""n"" />
</CmCommands>
</Commands>";
XDocument x = XDocument.Parse(xml);
Debug.Print(x.Elements().First().Elements().First().Attributes().Last().Value);
// Commands ^ CmCommands ^ Remark ^
That is, word for word, the last attribute of the first child of the first element.
You can also query for element/attribute names, like:
Debug.Print(x.Descendants(XName.Get("CmCommands", "")).First().Attribute(XName.Get("Remark", "")).Value);
And of course you can use all of the Linq goodness like Where, Select, Any, All etc.
Note: replace XDocument.Parse with XDocument.Load if appropriate etc.

I've not tested this but you should be able to do all of this in the XPath expression. Something like this:
//#*[contains(node-name(.), 'name')][last()]
This will return only the last attribute with the string name anywhere in its name.
If you only want the last attribute, irrespective of it's name, use this:
//#*[last()]

Look at class XmlAttributeCollection. You can get this collection by reading property Attributes of XmlNode. Just get the last by index.

Instead of .First(), use an extension method like this:
public static T LastOrDefault<T>(this IEnumerable<T> list)
{
T val = null;
foreach(T item in list)
{
val = item;
}
return val;
}