Extension methods for XPath 2.0 in .NET (C#)

.NET provides easy use of XPath with the Select(...) and SelectSingleNode(...) methods on XPathNavigator.

This blog post will show how you can use XmlPrime to add similar methods to provide XPath 2.0 support on XPathNavigator also.

This .NET 3.5 is required as this example uses extension methods.

First download and install XmlPrime, then in you project add a reference to the installed XmlPrime dll.

Now create a class with the following code:

using XmlPrime;
using System.Xml.XPath;

namespace xp.ExtensionMethods
{
   public static class XPathNavigatorExtensions
   {
      public static XPathNavigator SelectSingleNode2(
         this XPathNavigator navigator,
         string expression)
      {
         var compiledExpression = XPath.Compile(expression, navigator.NameTable);
         var item = compiledExpression.EvaluateToItem((XPathItem)navigator);
         return (XPathNavigator)item;
      }
   }
}

This will add a method to XPathNavigator, so you can then use XPath 2.0 in .NET just by typing:

navigator.SelectSingleNode2("/foo/bar[matches(.,'[a-z]')]")

wherever you would have used navigator.SelectSingleNode(...), but now you can use all the XPath 2.0 functionality; for example regular expression functions.

Implementing an equivalent of navigator.Select(...) and similar functions on XmlNode is equally straightforward.

We plan to include such extension methods in a the XmlPrime library in a future release.