XSLT Processing in .NET
This article is meant to help XML developers understand the different
ways XSLT transformations can be performed using the .NET framework. It
alsos describe how to use various input sources for an XSLT
transformation. In .NET, the
class is used for transforming XML data using an XSLT stylesheet.
System.Xml.Xsl.XslTransform supports the XSLT 1.0 syntax,
Input and Output Data Sources to the
There are several classes that may be used to read XML and XSLT
documents for a transformation. The most versatile of these is the
System.Xml.XmlReader class. Since
System.Xml.XmlReader is an abstract class, another class must
inherit from it. The first class of this type is
System.Xml.XmlTextReader, which reads character streams and
checks that XML is well-formed, but does not validate the XML against a
DTD or schema.
The second class that inherits from
System.Xml.XmlNodeReader, which allows data to be read
from any XML Document Object Model (DOM) API; for example,
not have to be a complete XML document; it may be a child node.
The third type of
XmlReader class is
System.Xml.XmlValidatingReader, a validating reader capable
of ensuring XML data conforms to a DTD, XML-Data Reduced (XDR) schema, or
W3C XML Schema.
// Load the String into a TextReader System.IO.TextReader tr = new System.IO.StreamReader("numbers.xsl"); // Use that TextReader as the Source for the XmlTextReader System.Xml.XmlReader xr = new System.Xml.XmlTextReader(tr); // Create a new XslTransform class System.Xml.Xsl.XslTransform trans = new System.Xml.Xsl.XslTransform(); // Load the XmlReader StyleSheet into the XslTransform class trans.Load(xr);
Another type of input class is
System.Xml.XPath.XPathNavigator or any class that implements
System.Xml.XPath.IXPathNavigable interface, including
System.Xml.XPath.XPathNavigator is based on the XPath data
model and provides the methods needed to implement XPath queries over any
System.Xml.XPath.XPathDocument is the fastest of such
classes, because it's read only, and is the preferred class when the speed
of XSLT transformations is the highest priority.
System.Xml.XmlDocument is the second most efficient class;
XMLDataDocument is not recommended for performing XSLT
System.Xml.XPath.IXPathNavigable may be
implemented against any data source, allowing any imaginable type of data
to be used as the source in an XSLT transformation.
// The following code may be appended to the preceding example // Create a new XPathDocument, loading the source from a file System.Xml.XPath.XPathDocument xp = new System.Xml.XPath.XPathDocument("numbers.xml"); // Create the Navigator System.Xml.XPath.XPathNavigator xpn = xp.CreateNavigator();
XslTransform class requires the source of the XML or
XSLT data to be an
Transform methods of the
System.Xml.Xsl.XslTransform class do not provide an
overloaded method for directly processing a
Stream, but the
example below demonstrates an indirect method to use a
MemoryStream as the source location of the XML data and XSLT
// Create a Stream and show how it would be used as the source // This is only a sample since no data exists in the stream. System.IO.Stream st = new System.IO.MemoryStream(); // You would populate the Stream with the XML File here and set the position to 0 st.Position = 0; // Using the Stream, load it into an XPathDocument System.Xml.XPath.XPathDocument xp = new System.Xml.XPath.XPathDocument(st); // Now do the same with the Xslt document System.IO.Stream XSLTStream = new System.IO.MemoryStream(); // You would populate the Stream with the XSLT File here and set the position to 0 st.Position = 0; // Use an XmlReader and pass in a Stream as the Source System.Xml.XmlReader xsltXR = new System.Xml.XmlTextReader(XSLTStream); // The XmlReader may be passed into the Load Method of XslTransformm
The line containing the initialization of the
just to demonstrate the
MemoryStream constructor; it is still
necessary to populate the data. One other source we may wish to use for
XML and XSLT documents is a document retrieved from a URL, in the form of
a string along with an optional
is the most efficient method to load the source from an existing file.
xsl:output element is sometimes ignored depending on
the type of output class used; if, for example, the output class is either
XmlWriter or an
XmlReader class. For a
detailed description of which attributes are supported on
xsl:output and the classes that support them please read the
from an XslTransform" section of the MSDN documentation.
The minimum requirements to perform an XSLT transformation are an XML
document, an XSLT document, and a valid object to handle the output. In
the example below, an
XPathDocument and stylesheet will be
loaded from a file, and output directed to the system console.
// Create the XslTransform. System.Xml.Xsl.XslTransform xslt = new System.Xml.Xsl.XslTransform(); // Load the stylesheet. xslt.Load("numbers.xsl"); // Load the XML data file. System.Xml.XPath.XPathDocument doc = new System.Xml.XPath.XPathDocument("numbers.xml"); // Create the XmlTextWriter to output to the console. System.Xml.XmlTextWriter writer = new System.Xml.XmlTextWriter(System.Console.Out); // Transform the file. xslt.Transform(doc, null, writer); // Be careful when using the console, // closing it will not allow you to write any // additional information to it writer.Close();
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