Develop Reference

How to select child node with XPath

I'm trying to get values from a XML document using the iXF format, but I'm having some issues with the XPath syntax.
I have the following XML document
<SOAP_ENV:Envelope xmlns:NS2="http://www.ixfstd.org/std/ns/core/classBehaviors/links/1.0" xmlns:NS1="CATIA/V5/Electrical/1.0" xmlns:tns="IXF_Schema.xsd" xmlns:ixf="http://www.ixfstd.org/std/ns/core/1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:SOAP_ENV="http://schemas.xmlsoap.org/soap/envelope/" xsi:schemaLocation="IXF_Schema.xsd ElectricalSchema.xsd">
<SOAP_ENV:Body>
<ixf:object id="Electrical Physical System00000089.1" xsi:type="tns:Harness">
<tns:Name>Electrical Physical System00000089.1</tns:Name>
</ixf:object>
<ixf:object id="X10(1)//X11(1)" xsi:type="tns:Wire">
<tns:Name>X10(1)//X11(1)</tns:Name>
<NS1:Wire>
<NS1:Length>763,752mm</NS1:Length>
<NS1:Color>RD</NS1:Color>
<NS1:OuterDiameter>1,32mm</NS1:OuterDiameter>
</NS1:Wire>
</ixf:object>
</SOAP_ENV:Body>
</SOAP_ENV:Envelope>
And i'm trying to find all the Wire objects and get the Name and Length values with the following code.
XmlDocument xlDocument = new XmlDocument();
xlDocument.Load(importFile);
XmlNamespaceManager nsManager = new XmlNamespaceManager(xlDocument.NameTable);
nsManager.AddNamespace("tns", "IXF_Schema.xsd");
nsManager.AddNamespace("xsi", "http://www.w3.org/2001/XMLSchema-instance");
nsManager.AddNamespace("ixf", "http://www.ixfstd.org/std/ns/core/1.0");
nsManager.AddNamespace("NS1", "CATIA/V6/Electrical/1.0");
nsManager.AddNamespace("NS2", "http://www.ixfstd.org/std/ns/core/classBehaviors/links/1.0");
//Get all wire objects
XmlNodeList wires = xlDocument.SelectNodes("descendant::ixf:object[#xsi:type = \"tns:Wire\"]", nsManager);
foreach (XmlNode wire in wires)
{
string wireName;
string wireLength;
XmlNode node = wire.SelectSingleNode("./tns:Name", nsManager);
wireName = node.InnerText;
XmlNode node1 = wire.SelectSingleNode("./NS1:Wire/NS1:Length", nsManager);
wireLength = node1.InnerText;
}
I can get the wireName value without any problems but the Length element selection always returns 0 matches and I can not figure out why. I also tried to only select the Wire element using the same syntax as the Name element ./NS1:Wire but that also returns 0 matches.

Your XML declares
xmlns:NS1="CATIA/V5/Electrical/1.0"
^^
Your C# declares a different namespacem
nsManager.AddNamespace("NS1", "CATIA/V6/Electrical/1.0")
^^
Make sure both namespaces match exactly.
Regarding your comment asking about the use of version numbers in namespaces...
It is an unfortunately common but certainly not widely accepted practice to include a version number in an XML namespace. Realize that by doing so, you're effectively saying that every namespaced XML component (element or attribute) should now be considered to differ from its counterpart in the old namespace. This is rarely what you want.
See also
Should I use a Namespace of an XML file to identify its version
What are the best practices for versioning XML schemas?

How to read xml string ignoring header?

I want to read a xml string ignoring the header and the comments.
To ignore the comments it's simples and I found a solution here.
But I'm not finding any solution to ignore the header.
Let me give an example:
Consider this xml:
<?xml version="1.0" encoding="iso-8859-1"?>
<!-- Some comments -->
<Tag Attribute="3">
...
</Tag>
I want to read the xml to a string obtaining just the element "Tag" and others elements but withou the "xml version" and the comments.
The element "Tag" is only an example. Could exist many others.
So, I want only this:
<Tag Attribute="3">
...
</Tag>
The code that I've come so far:
XmlReaderSettings settings = new XmlReaderSettings();
settings.IgnoreComments = true;
XmlReader reader = XmlReader.Create("...", settings);
xmlDoc.Load(reader);
And I'm not finding anything on XmlReaderSettings to do that.
Do I need to go node by node choosing only the ones I want? This setting does not exist?
EDIT 1:
Just to resume my problem. I need the contents of the xml to use in a CDATA of a WebService. When I'm sending comments or xml version, I'm getting an specific error of that part of xml. So I assume that when I read the xml without the version, header and comments I'll be good to go.

Here's a really simple solution.
using (var reader = XmlReader.Create(/*reader, stream, etc.*/)
{
reader.MoveToContent();
string content = reader.ReadOuterXml();
}

Well, it seems that there is no settings to ignore declaration, so I had to ignore it myself.
Here's the code I've written for those who might be interested:
private string _GetXmlWithoutHeadersAndComments(XmlDocument doc)
{
string xml = null;
// Loop through the child nodes and consider all but comments and declaration
if (doc.HasChildNodes)
{
StringBuilder builder = new StringBuilder();
foreach (XmlNode node in doc.ChildNodes)
if (node.NodeType != XmlNodeType.XmlDeclaration && node.NodeType != XmlNodeType.Comment)
builder.Append(node.OuterXml);
xml = builder.ToString();
}
return xml;
}

If you want to only get the Tag elements, you should just read the XML as normal, then find them using the XmlDocument's XPath capabilities.
For your xmlDoc object:
var nodes = xmlDoc.DocumentElement.SelectNodes("Tag");
You can then iterate through these like so:
foreach (XmlNode node in nodes) { }
Or, obviously, you could just put your SelectNodes query into the foreach loop, if you're never going to reuse the nodes object.
This will return all Tag elements within your XML document, and you can do whatever you see fit with them.
There's no need to ever encounter comments while using XmlDocument if you don't want to, and you're not going to end up getting results including either the header or the comments. Is there a particular reason you're trying to remove pieces of the XML before you begin parsing it?
Edit: Based on your edit, it seems like you're having a problem with the header giving an error when you try to pass it. You probably shouldn't straight-up remove the header, so your best option might be to change the header to one that you know works. You can change the header (declaration) like so:
XmlDeclaration xmlDeclaration;
xmlDeclaration = yourDocument.CreateXmlDeclaration(
yourVersion,
yourEncoding,
isStandalone);
yourDocument.ReplaceChild(xmlDeclaration, doc.FirstChild);

How to access an XML element in a single go?

I have an XML string like below:
<root>
<Test1>
<Result time="2">ProperEnding</Result>
</Test1>
<Test2></Test2>
I have to operate on these elements. Most of the time the elements are unique within their parent element. I am using XDocument. I can remember that there is a way to access an element like this.
XNode resultTest1 = GetNodes("/root//Test1//result")
But I forgot it. It is possible to access the same using linq:
doc.root.Elements.etc.etc.
But I want it using a single string as shown above. Can anybody say how to make it?

Descendants() will skip any number level of intermediate nodes, e.g. this will skip over root and Test1:
doc.Decendants("Result")
Also note that you can use XPath with Linq2Xml as well, e.g. XPathSelectElements
doc.XPathSelectElements("/root/Test1/Result");
You can skip intermediate levels of the hierarchy with // (or use // at the start of the xpath string to skip the root)
"/root//Result"
One caveat - Xml is case sensitive , so Result and result are not the same element.

The string you're referring to ("/root//Test1//result") is an XPath expression.
You can use it with LINQ to XML classes (like XDocument) using XPathEvaluate, XPathSelectElement, and XPathSelectElements extension methods.
You can find more info about these methods on MSDN: http://msdn.microsoft.com/en-us/library/vstudio/system.xml.xpath.extensions_methods(v=vs.90).aspx
To make them work, you need using System.Xml.XPath at the top of your file and System.Xml.Linq.dll assembly referenced (which is probably already there).

You can try to load your xml using XDocument:
// loads xml file with root element
XDocument xml = XDocument.Load("filename.xml");
Now you can append LINQ statements to your xml variable like this:
var retrieveSomeSpecificDataLikeListOfElementsAsAnonymousObjects = xml.Descendants("parentNodeName").Select(node => new { SomeSpecialValueYouWant = node.Element("elementNameUnderParentNode").Value }).ToList();
You can mix and do whatever you want - above is just an example.

Is this what you looking?
XmlDocument xmlDocument = new XmlDocument();
xmlDocument.LoadXml("YourXML");
XmlNodeList xmlNodes = xmlDocument.SelectNodes("/root/Test1/result");

Parse XDocument without having to keep specifying the default namespace

I have some XML data (similar to the sample below) and I want to read the values in code.
Why am I forced to specify the default namespace to access each element? I would have expected the default namespace to be used for all elements.
Is there a more logical way to achieve my goal?
Sample XML:
<?xml version="1.0" encoding="UTF-8"?>
<ReceiptsBatch xmlns="http://www.secretsonline.gov.uk/secrets">
<MessageHeader>
<MessageID>00000173</MessageID>
<Timestamp>2009-10-28T16:50:01</Timestamp>
<MessageCheck>BX4f+RmNCVCsT5g</MessageCheck>
</MessageHeader>
<Receipts>
<Receipt>
<Status>OK</Status>
</Receipt>
</Receipts>
</ReceiptsBatch>
Code to read xml elements I'm after:
XDocument xDoc = XDocument.Load( FileInPath );
XNamespace ns = "http://www.secretsonline.gov.uk/secrets";
XElement MessageCheck = xDoc.Element(ns+ "MessageHeader").Element(ns+"MessageCheck");
XElement MessageBody = xDoc.Element("Receipts");

As suggested by this answer, you can do this by removing all namespaces from the in-memory copy of the document. I suppose this should only be done if you know you won't have name collisions in the resulting document.
/// <summary>
/// Makes parsing easier by removing the need to specify namespaces for every element.
/// </summary>
private static void RemoveNamespaces(XDocument document)
{
var elements = document.Descendants();
elements.Attributes().Where(a => a.IsNamespaceDeclaration).Remove();
foreach (var element in elements)
{
element.Name = element.Name.LocalName;
var strippedAttributes =
from originalAttribute in element.Attributes().ToArray()
select (object)new XAttribute(originalAttribute.Name.LocalName, originalAttribute.Value);
//Note that this also strips the attributes' line number information
element.ReplaceAttributes(strippedAttributes.ToArray());
}
}

You can use XmlTextReader.Namespaces property to disable namespaces while reading XML file.
string filePath;
XmlTextReader xReader = new XmlTextReader(filePath);
xReader.Namespaces = false;
XDocument xDoc = XDocument.Load(xReader);

This is how the Linq-To-Xml works. You can't find any element, if it is not in default namespace, and the same is true about its descendants. The fastest way to get rid from namespace is to remove link to the namespace from your initial XML.

The theory is that the meaning of the document is not affected by the user's choice of namespace prefixes. So long as the data is in the namespace http://www.secretsonline.gov.uk/secrets, it doesn't matter whether the author chooses to use the prefix "s", "secrets", "_x.cafe.babe", or the "null" prefix (that is, making it the default namespace). Your application shouldn't care: it's only the URI that matters. That's why your application has to specify the URI.

Note that the element Receipts is also in namespace http://www.secretsonline.gov.uk/secrets, so the XNamespace would also be required for the access to the element:
XElement MessageBody = xDoc.Element(ns + "Receipts");
As an alternative to using namespaces note that you can use "namespace agnostic" xpath using local-name() and namespace-uri(), e.g.
/*[local-name()='SomeElement' and namespace-uri()='somexmlns']
If you omit the namespace-uri predicate:
/*[local-name()='SomeElement']
Would match ns1:SomeElement and ns2:SomeElement etc. IMO I would always prefer XNamespace where possible, and the use-cases for namespace-agnostic xpath are quite limited, e.g. for parsing of specific elements in documents with unknown schemas (e.g. within a service bus), or best-effort parsing of documents where the namespace can change (e.g. future proofing, where the xmlns changes to match a new version of the document schema)

How to merge two XmlDocuments in C#

I want to merge two XmlDocuments by inserting a second XML doc to the end of an existing Xmldocument in C#. How is this done?

Something like this:
foreach (XmlNode node in documentB.DocumentElement.ChildNodes)
{
XmlNode imported = documentA.ImportNode(node, true);
documentA.DocumentElement.AppendChild(imported);
}
Note that this ignores the document element itself of document B - so if that has a different element name, or attributes you want to copy over, you'll need to work out exactly what you want to do.
EDIT: If, as per your comment, you want to embed the whole of document B within document A, that's relatively easy:
XmlNode importedDocument = documentA.ImportNode(documentB.DocumentElement, true);
documentA.DocumentElement.AppendChild(importedDocument);
This will still ignore things like the XML declaration of document B if there is one - I don't know what would happen if you tried to import the document itself as a node of a different document, and it included an XML declaration... but I suspect this will do what you want.

Inserting an entire XML document at the end of another XML document is actually guaranteed to produce invalid XML. XML requires that there be one, and only one "document" element. So, assuming that your files were as follows:
A.xml
<document>
<element>value1</element>
<element>value2</element>
</document>
B.xml
<document>
<element>value3</element>
<element>value4</element>
</document>
The resultant document by just appending one at the end of the other:
<document>
<element>value1</element>
<element>value2</element>
</document>
<document>
<element>value3</element>
<element>value4</element>
</document>
Is invalid XML.
Assuming, instead, that the two documents share a common document element, and you want to insert the children of the document element from B into A's document element, you could use the following:
var docA = new XmlDocument();
var docB = new XmlDocument();
foreach (var childEl in docB.DocumentElement.ChildNodes) {
var newNode = docA.ImportNode(childEl, true);
docA.DocumentElement.AppendChild(newNode);
}
This will produce the following document given my examples above:
<document>
<element>value1</element>
<element>value2</element>
<element>value3</element>
<element>value4</element>
</document>

This is the fastest cleanest way to merge xml documents.
XElement xFileRoot = XElement.Load(file1.xml);
XElement xFileChild = XElement.Load(file2.xml);
xFileRoot.Add(xFileChild);
xFileRoot.Save(file1.xml);

Bad news. As long as the xml documents can have only one root element you cannot just put content of one document at the end of the second. Maybe this is what you are looking for? It shows how easily you can merge xml files using Linq-to-XML
Alternatively if you are using XmlDocuments you can try make it like this:
XmlDocument documentA;
XmlDocument documentB;
foreach(var childNode in documentA.DocumentElement.ChildNodes)
documentB.DocumentElement.AppendChild(childNode);