INFO: Roadmap for Programming XML with the DOM-Model Parser in the .NET Framework

This article provides a roadmap for programming XML with the Document Object Model (DOM) parser of the .NET Framework. To help with learning a Microsoft product or technology, roadmap articles provide links to useful information, including online documentation, Microsoft Knowledge Base articles, and white papers.

This article assumes a familiarity with the Worldwide Web Consortium (W3C) DOM standard.

Overview

The .NET Framework provides two ways to parse XML data:

• Pull-model parser (XmlReader and related classes)
• DOM-model parser (XmlDocument and related classes)

The pull model provides forward-only, read-only, noncached access to XML data. The DOM model provides in-memory, random, read/write access to XML data. This article covers the DOM-model parser of the .NET Framework. This implementation is compliant with the Worldwide Web Consortium (W3C) DOM Level 1 and Level 2 specifications. The DOM-model parser lets you programmatically manipulate the in-memory representation of the XML data.

XML in the .NET Framework is implemented under the System.Xml namespace. The following DOM-related classes provide ways to access, modify, and delete content in XML documents by using the DOM model:

• The XmlNode class represents a single node. As shown in the DOM hierarchy (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconxmldocumentobjectmodeldomhierarchy.asp) diagram, this abstract class acts as the base class for most of the DOM classes. (This diagram also shows the equivalent W3C names of the DOM classes.) XmlNode contains the majority of methods and properties that are needed to work with the data in an XML node. The XmlNodeList class represents a set of ordered nodes. The XmlNamedNodeMap class can be used to handle unordered sets of nodes.
• The XmlDocument class represents the DOM document. This is an in-memory representation of XML data that enables navigation and editing, and can be used to load and manipulate XML documents. The XmlNodeChangedEventArgs class handles event handlers registered on an XmlDocument.
• The XmlAttribute class represents an attribute; this class lets you access and edit attributes of the nodes. The XmlAttributeCollection class represents a collection of attributes.
• The XmlElement class represents an element. This class is derived from XmlLinkedNode, which provides access to previous and subsequent nodes.

System.Xml also provides several other classes, such as XmlText, XmlDeclaration, XmlComment, and XmlWhitespace, that map to a W3C DOM structure. For a complete list, see "Types of XML Nodes" at the following MSDN Web site:

Key Concepts and QuickStarts

The QuickStart tutorials are the fastest way to understand what the .NET Framework technology offers leading-edge developers. Following are links to relevant samples and documentation for DOM-model processing of XML.

HOW TO Articles

Microsoft Knowledge Base HOW TO articles provide step-by-step instructions for accomplishing specific tasks.

Typical steps in DOM-model processing include loading the XML data into an XmlDocument instance, manipulating or querying the data by using the DOM classes, and then persisting the results. The following Knowledge Base articles provide code samples for performing these activities: You can also run XSL transformations (XSLT), validate XML documents against schemas, and serialize and deserialize XML data by using the System.Xml classes in .NET Framework. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

Guidelines

Your choice of parser models may depend on your application's requirements. Note that the DOM-model parser loads the whole XML document into memory whereas the pull model loads one node at a time. The pull model consumes less memory but does not provide random access to data.

The DOM model is suited for applications that require random, read/write access to the data where memory consumption is not a factor. The pull model is suited for applications that require speed and memory conservation. Under many circumstances, the required solution may be a hybrid of these two models. For example, if part of a very large XML document needs to be manipulated, it may be efficient to use the pull model to read it, and then construct a DOM with only the data needed for additional modification.

Troubleshooting

If you experience problems and want assistance, the best place to start is at the Microsoft Product Support Services Web site: You have several options to find answers to your questions. You can search the Microsoft Knowledge Base, post your questions or share your experiences on Microsoft newsgroups, obtain the latest service packs and news about a specific product, or contact Microsoft Product Support.