Chapter 17. XML

XML (Extensible Markup Language) is a simple, portable, and flexible way to represent data in a structured format. XML is used in a myriad of ways, from acting as the foundation of web-based messaging protocols like SOAP, to being one of the more popular ways to store configuration data (such as the web.config, machine.config, or security.config files in the .NET Framework). Microsoft recognized the usefulness of XML to developers and has done a nice job of giving the developer choices around the tradeoffs one encounters when using XML. Sometimes you want to simply run though an XML document looking for a value in a read-only cursor-like fashion, and other times you need to be able to randomly access various pieces of the document. Microsoft provides classes like XmlTextReader and XmlTextWriter for lighter access and XmlDocument for full DOM (Document Object Model) processing support. It is likely that if you use .NET you will be dealing with XML to one degree or another, and in this chapter we explore some of the uses for XML and XML-based technologies like XPath and XSLT, as well as explore topics like validation of XML and transformation of XML to HTML.