XSLT Transformations with the XslTransform Cl...

素行 2007-01-11

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.NET Framework Developer‘s Guide

XSLT Transformations with the XslTransform Class

The goal of the Extensible Stylesheet Language Transformation (XSLT) is to transform the content of a source XML document into another document that is different in format or structure. For example, to transform XML into HTML for use on a Web site or to transform it into a document that contains only the fields required by an application. This transformation process is specified by the W3C XSL Transformations (XSLT) Version 1.0 recommendation located at www.w3.org/TR/xslt. In the .NET Framework, the XslTransform class, found in the System.Xml.Xsl namespace, is the XSLT processor that implements the functionality of this specification. There are a small number of features that have not been implemented from the W3C XSLT Version 1.0 recommendation, listed in Outputs from an XslTransform. The following figure shows the transformation architecture of the .NET Framework.

Transformation Architecture

The XSLT recommendation uses XPath to select parts of an XML document, where XPath is a query language used to navigate nodes of a document tree. As shown in the diagram, the .NET Framework implementation of XPath is used to select parts of XML stored in several classes, such as an XmlDocument, an XmlDataDocument, and an XPathDocument. An XPathDocument is an optimized XSLT data store, and when used with XslTransform, it provides XSLT transformations with good performance.

The following table list commonly used classes when working with XslTransform and XPath and their function.

Class or Interface	Function
XPathNavigator	It is an API that provides a cursor style model for navigating over a store, along with XPath query support. It does not provide editing of the underlying store. For editing, use the XmlDocument class.
IXPathNavigable	It is an interface that provides a CreateNavigator method to an XPathNavigator for the store.
XmlDocument	It enables editing of this document. It implements IXPathNavigable, allowing document-editing scenarios where XSLT transformations are subsequently required. For more information, see XmlDocument Input to XslTransform.
XmlDataDocument	It is derived from the XmlDocument. It bridges the relational and XML worlds by using a DataSet to optimize storage of structured data within the XML document according to specified mappings on the DataSet. It implements IXPathNavigable, allowing scenarios where XSLT transformations can be performed over relational data retrieved from a database. For more information, see XML Integration with Relational Data and ADO.NET.
XPathDocument	This class is optimized for XslTransform processing and XPath queries, and it provides a read-only high performance cache. It implements IXPathNavigable and is the preferred store to use for XSLT transformations.
XPathNodeIterator	It provides navigation over XPath node sets. All XPath selection methods on the XPathNavigator return an XPathNodeIterator. Multiple XPathNodeIterators can be created over the same store each representing a selected set of nodes.

The following code example loads an XSL style sheet, reads a file called mydata.xml into an XPathDocument, and performs a transformation on the data on a fictitious file called myStyleSheet.xsl, sending the formatted output to the console.

[Visual Basic]
Imports System
Imports System.IO
Imports System.Xml
Imports System.Xml.XPath
Imports System.Xml.Xsl
Public Class Sample
Private filename As [String] = "mydata.xml"
Private stylesheet As [String] = "myStyleSheet.xsl"
Public Shared Sub Main()
Dim xslt As New XslTransform()
xslt.Load(stylesheet)
Dim xpathdocument As New XPathDocument(filename)
Dim writer As New XmlTextWriter(Console.Out)
writer.Formatting = Formatting.Indented
xslt.Transform(xpathdocument, Nothing, writer, Nothing)
End Sub ‘Main
End Class ‘Sample
[C#]
using System;
using System.IO;
using System.Xml;
using System.Xml.XPath;
using System.Xml.Xsl;
public class Sample
{
private const String filename = "mydata.xml";
private const String stylesheet = "myStyleSheet.xsl";
public static void Main()
{
XslTransform xslt = new XslTransform();
xslt.Load(stylesheet);
XPathDocument xpathdocument = new
XPathDocument(filename);
XmlTextWriter writer = new XmlTextWriter(Console.Out);
writer.Formatting=Formatting.Indented;
xslt.Transform(xpathdocument, null, writer, null);
}
}