C# 4 and .NET 4

922 ❘ ChaPTer 33 mAnipulAtinG xml
Nodes can be inserted before or after a selected node. The nodes can also be changed, and they can be
deleted. If you have changes that have to be done to large numbers of nodes, using the XPathNavigator
created from an XmlDocument may be your best choice.
The system.Xml.Xsl namespace
The System.Xml.Xsl namespace contains the classes that the .NET Framework uses to support XSL
transforms. The contents of this namespace are available to any store whose classes implement the
IXPathNavigable interface. In the .NET Framework, that would currently include XmlDocument,
XmlDataDocument, and XPathDocument. Again, just as with XPath, use the store that makes the most
sense. If you plan to create a custom store, such as one using the file system and you want to be able to do
transforms, be sure to implement the IXPathNavigable interface in your class.
XSLT is based on a streaming pull model. Because of this, you can chain several transforms together. You
could even apply a custom reader between transforms if needed. This allows a great deal of flexibility in design.
Transforming XMl
The first example you will look at takes the books.xml document and transforms it into a simple HTML
document for display, using the XSLT file books.xsl. (This code is in the XSLSample01 folder.) You will
need to add the following using statements:
using System.IO;
using System.Xml.Xsl;
using System.Xml.XPath;
The following is the code to perform the transform:
private void button1_Click(object sender, EventArgs e)
{
XslCompiledTransform trans = new XslCompiledTransform();
trans.Load("books.xsl");
trans.Transform("books.xml", "out.html");
webBrowser1.Navigate(AppDomain.CurrentDomain.BaseDirectory + "out.html");
}
code download XslSample01.sln
A transform doesn’t get any simpler than this. First, a new XmlCompiledTransform object is created. It
loads the books.xsl transform document and then performs the transform. In this example, a string with
the filename is used as the input. The output is out.html. This file is then loaded into the web browser
control used on the form. Instead of using the filename books.xml as the input document, you can use an
IXPathNavigable-based object. This would be any object that can create an XPathNavigator.
After the XmlCompiledTransform object is created and the stylesheet is loaded, the transform is performed.
The Transform method can take just about any combination of IXPathNavigable objects, Streams,
TextWriters, XmlWriters, and URIs as parameters. This allows a great deal of flexibility on transform
flow. You can pass the output of one transform in as the input to the next transform.
XsltArgumentLists and XmlResolver objects are also included in the parameter options. We look at the
XsltArgumentList object in the next section. XmlResolver-based objects are used to resolve items that are
external to the current document. This could be things such as schemas, credentials, or, of course, stylesheets.
The books.xsl document is a fairly straightforward stylesheet. The document looks like this:
Price List
www.it-ebooks.info