XmlDocument Class - .NET Framework System.Xml

Class XmlDocument

Represents an XML document object model (DOM) that can be loaded and manipulated.

Summary

The XmlDocument class provides a way to load, navigate, and modify XML documents in memory. It implements the System.Xml.XmlLoadLoad interface, offering a comprehensive set of methods and properties for working with XML data. This class is fundamental for many XML processing tasks in .NET.

Syntax

public class XmlDocument : XmlNode, IXmlSerializable

Remarks

XmlDocument is part of the .NET Framework's XML Document Object Model (DOM) implementation. It allows you to parse an XML document into a tree structure, enabling you to access and manipulate individual nodes (elements, attributes, text, etc.). Key features include:

Loading XML from files, streams, or strings.
Navigating the XML tree using methods like GetElementById, SelectSingleNode, and SelectNodes.
Modifying the XML tree by creating, adding, removing, or changing nodes.
Saving the modified XML back to a file, stream, or string.
Supporting the XPath query language for efficient data retrieval.

Note

For performance-critical scenarios or very large XML documents, consider using System.Xml.XmlReader and System.Xml.XmlWriter for forward-only, read-only access, or the System.Xml.Linq namespace (LINQ to XML) which often provides a more modern and intuitive API.

Constructor Summary

Constructor	Description
`XmlDocument()`	Initializes a new instance of the `XmlDocument` class.
`XmlDocument(XmlImplementation impl)`	Initializes a new instance of the `XmlDocument` class with the specified `XmlImplementation`.

Properties

Property	Description
`DocumentElement`	Gets the root element of the document (`XmlElement`).
`DocumentType`	Gets the document type node (`XmlDocumentType`).
`Implementation`	Gets an `XmlImplementation` object for the current document.
`Name`	Gets the name of the node. For `XmlDocument`, this is usually `#document`.
`NodeType`	Gets the node type. For `XmlDocument`, this is `XmlNodeType.Document`.
`OwnerDocument`	Gets the `XmlDocument` to which this node belongs. For the document node itself, this is `null`.
`Schema`	Gets or sets the schema against which the XML document is validated.
`Supports (inherited)`	Gets a value indicating whether the DOM implementation supports the specified feature.
`Value (inherited)`	Gets or sets the value of the node. For `XmlDocument`, this is `null`.

Methods

Method	Description
`CreateAttribute(string name)`	Creates an `XmlAttribute`.
`CreateCDataSection(string data)`	Creates an `XmlCDataSection`.
`CreateComment(string data)`	Creates an `XmlComment`.
`CreateDocumentFragment()`	Creates an `XmlDocumentFragment`.
`CreateElement(string prefix, string localName, string namespaceURI)`	Creates an `XmlElement` with the specified prefix, local name, and namespace URI.
`CreateElement(string tagName)`	Creates an `XmlElement` with the specified tag name.
`CreateEntityReference(string name)`	Creates an `XmlEntityReference`.
`CreateNavigator()`	Creates an `XPathNavigator` object for navigating this document.
`CreateProcessingInstruction(string target, string data)`	Creates an `XmlProcessingInstruction`.
`CreateSignificantWhitespace(string whitespace)`	Creates an `XmlSignificantWhitespace` node.
`CreateTextNode(string text)`	Creates an `XmlText` node.
`CreateWhitespace(string whitespace)`	Creates an `XmlWhitespace` node.
`GetElementById(string id)`	Retrieves an `XmlElement` with the specified `ID` attribute value.
`GetElementsByTagName(string name)`	Returns an `XmlNodeList` containing all the descendant elements with the given tag name.
`Load(string filename)`	Loads the XML document from the specified file.
`Load(XmlReader reader)`	Loads the XML document from the specified `XmlReader`.
`LoadXml(string xml)`	Loads and parses the specified markup into the `XmlDocument`.
`Save(string filename)`	Saves the XML document to the specified file.
`Save(XmlWriter w)`	Saves the XML document to the specified `XmlWriter`.
`SelectSingleNode(string xpath)`	Selects the first `XmlNode` that matches the XPath query.
`SelectNodes(string xpath)`	Selects a list of all descendant nodes that match the XPath query.
`WriteContentTo(XmlWriter w)`	Saves all the children of the current node to the specified `XmlWriter`.
`WriteTo(XmlWriter w)`	Saves the current node and all its children to the specified `XmlWriter`.

Example

using System;
using System.Xml;

public class Example
{
    public static void Main(string[] args)
    {
        // Create an XML document
        XmlDocument doc = new XmlDocument();

        // Load XML from a string
        doc.LoadXml("<catalog><book id='bk101'>" +
                    "<author>Gambardella, Matthew</author>" +
                    "<title>XML Developer's Guide</title>" +
                    "<genre>Computer</genre>" +
                    "<price>44.95</price>" +
                    "<publish_date>2000-10-01</publish_date>" +
                    "<description>An in-depth look at creating applications " +
                    "with XML.</description>" +
                    "</book></catalog>");

        // Get the root element
        XmlElement root = doc.DocumentElement;

        // Select a node using XPath
        XmlNode bookTitle = doc.SelectSingleNode("//book/@title");
        if (bookTitle != null)
        {
            Console.WriteLine("Book Title: " + bookTitle.InnerText);
        }

        // Get elements by tag name
        XmlNodeList bookNodes = doc.GetElementsByTagName("book");
        Console.WriteLine("Number of books: " + bookNodes.Count);

        // Add a new element
        XmlElement newBook = doc.CreateElement("book");
        newBook.SetAttribute("id", "bk102");

        XmlElement author = doc.CreateElement("author");
        author.InnerText = "Ralls, Kim";
        newBook.AppendChild(author);

        XmlElement title = doc.CreateElement("title");
        title.InnerText = "Midnight Rain";
        newBook.AppendChild(title);

        root.AppendChild(newBook);

        // Save the modified document to a string
        Console.WriteLine("\nModified XML:");
        Console.WriteLine(doc.OuterXml);
    }
}