XPath is the W3C's general query language specification for addressing parts of an XML document. The .NET Framework implementation of XPath conforms to the World Wide Web Consortium (W3C) XML Path Language (XPath) Version 1.0 specification.

For fast, high-performance XML document processing using XSLT, use the XPathDocument class. You can think of the XPathDocument class as similar to the XML DOM, but highly optimized for XSLT processing and the XPath data model. However, unlike the W3C XML DOM classes, the XPathDocument class does not maintain node identity, nor does it do all the rule and validation checking required by the DOM classes.

You can also perform XPath queries against an XmlDocument or XmlDataDocument class. If you use one of these two classes, then you need to use the SelectNodes and SelectSingleNode methods of the XmlNode class.