XmlDocument

XmlDocument is a class in the .NET Framework and .NET Core that represents an XML document as a Document Object Model (DOM). It provides a programmatic representation of the document's tree structure, enabling code to read, navigate, modify, and write XML. XmlDocument inherits from XmlNode and serves as the root of the document tree.

Key features include constructing or loading the document from a file, stream, string, or XmlReader; accessing the root element via DocumentElement; creating new nodes with factory methods such as CreateElement, CreateAttribute, CreateTextNode, and other node types; and saving changes back to a file or stream using Save. It also supports XPath queries with SelectNodes and SelectSingleNode.

XmlDocument provides properties to access or alter the document content, such as InnerXml and OuterXml, and supports events like NodeChanged, NodeInserted, NodeRemoved, and NodeRenamed to observe mutations. It offers options for whitespace handling via PreserveWhitespace and can be used with XmlNamespaceManager for namespace-aware XPath queries.

Usage considerations: XmlDocument operates in memory and is suitable for moderate-sized XML documents. For large files or streaming scenarios, alternatives such as XmlReader or the LINQ to XML API (XDocument) may be more appropriate. XmlDocument is commonly used in legacy codebases and in applications where DOM-style manipulation is desired.

Where applicable, the class is found in the System.Xml namespace. It interoperates with validation through XmlReaderSettings when loading, and with schemas via XML validation events if a validating reader is used. In modern projects, developers may prefer XDocument for a more functional, LINQ-based approach.