C# 12 in a Nutshell

Chapter 10. LINQ to XML

.NET provides a number of APIs for working with XML data. The primary choice for general-purpose XML document processing is LINQ to XML. LINQ to XML comprises a lightweight, LINQ-friendly XML document object model (DOM), plus a set of supplementary query operators.

In this chapter, we concentrate entirely on LINQ to XML. In Chapter 11, we cover the forward-only XML reader/writer, and in the online supplement, we cover the types for working with schemas and stylesheets. .NET also includes the legacy XmlDocument-based DOM, which we don’t cover.

Note

The LINQ to XML DOM is extremely well designed and highly performant. Even without LINQ, the LINQ to XML DOM is valuable as a lightweight façade over the low-level XmlReader and XmlWriter classes.

All LINQ to XML types are defined in the System.Xml.Linq namespace.

Architectural Overview

This section starts with a very brief introduction to the concept of a DOM, and then explains the rationale behind LINQ to XML’s DOM.

What Is a DOM?

Consider the following XML file:

<?xml version="1.0" encoding="utf-8"?>
<customer id="123" status="archived">
  <firstname>Joe</firstname>
  <lastname>Bloggs</lastname>
</customer>

As with all XML files, we start with a declaration and then a root element, whose name is customer. The customer element has two attributes, each with a name (id and status) and value ("123" and "archived"). Within customer, there are two child elements, firstname and lastname, each having simple text content ...