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Extensions.XPathEvaluate Method (XNode, String, IXmlNamespaceResolver)

 

Evaluates an XPath expression, resolving namespace prefixes using the specified IXmlNamespaceResolver.

Namespace:   System.Xml.XPath
Assembly:  System.Xml.Linq (in System.Xml.Linq.dll)

public static object XPathEvaluate(
	this XNode node,
	string expression,
	IXmlNamespaceResolver resolver
)

Parameters

node
Type: System.Xml.Linq.XNode

The XNode on which to evaluate the XPath expression.

expression
Type: System.String

A String that contains an XPath expression.

resolver
Type: System.Xml.IXmlNamespaceResolver

A IXmlNamespaceResolver for the namespace prefixes in the XPath expression.

Return Value

Type: System.Object

An object that contains the result of evaluating the expression. The object can be a bool, a double, a string, or an IEnumerable<T>.

You can use this method to evaluate XPath expressions that contain namespace prefixes.

Although the ordering of returned collections is not specified in the XML XPath Language 1.0 Recommendation, this extension method returns nodes in document order.

Note that nodes are returned in document order even when you use a reverse axis, such as preceding-sibling or ancestor-or-self.

The following example creates an XML tree that contains a namespace. It uses an XmlReader to read the XML document. It then gets an XmlNameTable from the XmlReader, and an XmlNamespaceManager from the XmlNameTable. It uses the XmlNamespaceManager when selecting an element.


                string markup =
@"<aw:Root xmlns:aw='http://www.adventure-works.com'>
    <aw:Child1 aw:Att='attdata'>child one data 1</aw:Child1>
</aw:Root>";
XmlReader reader = XmlReader.Create(new StringReader(markup));
XElement root = XElement.Load(reader);
XmlNameTable nameTable = reader.NameTable;
XmlNamespaceManager namespaceManager = new XmlNamespaceManager(nameTable);
namespaceManager.AddNamespace("aw", "http://www.adventure-works.com");
IEnumerable atts = (IEnumerable)root.XPathEvaluate("./aw:Child1/@aw:Att", namespaceManager);
IEnumerable<XAttribute> attList = atts.Cast<XAttribute>();
XAttribute att = attList.First();
Console.WriteLine(att);

This example produces the following output:

aw:Att="attdata"

.NET Framework
Available since 3.5
Silverlight
Available since 4.0
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