XML transformations in .NET - Part I

I have sufficiently commented the code for understanding and clarity but I will elaborate further on what’s going on.

First, notice that I have imported the necessary Namespaces.

Imports System
Imports System.IO
Imports System.Xml
Imports System.Xml.XPath
Imports System.Xml.Xsl

Second, all my processing is occurring within the scope of Page Load. In a real word business class application, code like this will most likely be encapsulated into reusable assemblies.

If you’ll notice, a StringWriter object was declared:

'Prepare StringWriter for results
Dim sw As StringWriter = New StringWriter()

The stringwriter variable “sw” will be used later to dump the HTML transformation results into. To perform a transformation, two documents are needed, the XSL and XML files. First, load up the XML document:

'Load xml file into XMLDoc
XMLDoc = New XPathDocument(Server.MapPath("computers.xml"))

I am loading my XML document into an XPathDocument object. The XPathDocument object is optimized for efficient XSLT performance.

Next I call the load() method of the XSLTransform class to load the xsl file:

'Load XSL
XSLTDoc = New XslTransform()
XSLTDoc.Load(Server.MapPath("computers.xsl"))

Now that we have both XML and XSL loaded into memory, calling the Transform() method of the XSLTransform object will do all the xslt processing for us.

'Transform XMLDoc and dump HTML results to stringwriter -> sw
XSLTDoc.Transform(XMLDoc, Nothing, sw)

The Transform() method is overloaded. In this case it accepts three parameters:

1. The XML document
2. An Argument list
3. The StringWriter

We are not using any arguments for this transformation so passing in “Nothing” is acceptable. Also, notice that we finally passed in the StringWriter object that was declared earlier. As I have stated, calling Transform() will populate the StringWriter with the HTML results. We can then use the results of the StringWriter for page output:

'Pull results out of stringwriter and populate literal
ltl_htmlResults.Text = sw.ToString()

So there you have it, basic XSLT Transformations in .NET. In Part 2 of XSLT Transformations, I’ll dig a little deeper into the XSLTransform class. We’ll examine the usage of XSL Arguments and Extension Objects, allowing our XSL templates to perform more dynamic operations on XML data.