#XPath

XPath is a query language for selecting nodes in XML documents. If LINQ is how .NET developers query collections, XPath is how the XML world queries document trees — and it's been doing it since 1999.

XPath is not a standalone tool. It's embedded in XSLT (for matching and selecting), in XQuery (as the navigation syntax), and available directly in .NET via XPathNavigator and PhoenixmlDb.

#What's Here

• Path Expressions — The core of XPath: navigating the document tree with /, //, predicates, and axes. This is where most of your day-to-day work happens.

• Functions — Comprehensive reference for XPath 4.0's 240+ built-in functions, organized by category: string, numeric, date/time, sequence, map, array, math, higher-order, and more.

• Operators and Comparisons — Arithmetic, comparison, logical operators, and the difference between value and general comparisons.

• Data Types — How XPath's type system works, type casting, and interaction with schema types.

#XPath by Example

Given this XML:

<catalog>
  <book isbn="978-0-123456-78-9" category="programming">
    <title>Effective C#</title>
    <author>Bill Wagner</author>
    <price currency="USD">39.99</price>
    <published>2017-03-15</published>
  </book>
  <book isbn="978-0-987654-32-1" category="data">
    <title>XML in a Nutshell</title>
    <author>Elliotte Harold</author>
    <price currency="USD">49.99</price>
    <published>2004-09-01</published>
  </book>
</catalog>
                              

Notice how XPath expressions are more concise than their LINQ equivalents — and they're portable across any XML tool, not just .NET.