XPathNavigator is the universal interface for XML access in the .NET framework. It provides a read-only, XPath-centric way to access XML data. All the major XML APIs in .NET (XmlDocument, XmlDataDocument, and XPathDocument) are capable of producing an XPathNavigator. XslTransform is the workhorse of XSLT in .NET and uses XPathDocument and XPathNavigator to efficiently process XML documents. In the last article of this series, we will branch out to data access and discuss the XML support of ADO.NET through the DataSet and XmlDataDocument classes.