Navigating a Non-XML Document with XPath

One of the most interesting and unique aspects of .NET’s XML implementation is the fact that you can read non-XML data as if it were XML by creating subclasses of its abstract types. You saw this already in XmlReader and XmlWriter.

Because you can read an XmlDocument from any XmlReader, it follows that you can call that XmlDocument’s SelectSingleNode( ) and CreateNavigator( ) methods to navigate the document via XPath. You can also create an XPathDocument from any XmlReader, and use its CreateNavigator( ) method. In addition to that, however, you can also create a custom implementation of XPathNavigator to navigate any source document with XPath.

Using a custom XmlReader

You’ve already created and used XmlPyxReader in Chapter 4. Since XmlPyxReader is just like any other instance of XmlReader, you can pass it to XPathDocument’s constructor and navigate it using XPath:

XmlReader reader = new XmlPyxReader(filename);
XPathDocument document = new XPathDocument(reader);

XPathNavigator navigator = document.CreateNavigator( );
XPathNodeIterator iterator = navigator.Select(xpathExpression);
Console.WriteLine("{0} nodes matched.", iterator.Count);
while (iterator.MoveNext( )) {
writer.Close( );

Using a custom XPathNavigator

The next possibility is to skip over the custom XmlReader and go directly to a custom XPathNavigator. Like custom XmlReaders, custom XPathNavigators have numerous methods ...

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