C# and XSLT extension objects

Recently, I needed to transform an XML feed using C#. I wrote the XSLT script and it all worked ok.

One of the parts of the page took a TITLE and passed it to a Javascript function which then passed it to a flash file. This one particular record had a single quote, which as all developers know, will break everything within a 3 mile radius.

Trawling the MSDN rainforest led me to discover that you could pass parameters from the C# class which was carrying out the transformation, so I wondered if you could call methods in C# from the XSLT and behold you could.

The key was the AddExtensionObject method.

// Load XML document
XPathDocument myXPathDoc = new XPathDocument("c:/myfile.xml") ;

// Create trans object
XslCompiledTransform myXslTrans = new XslCompiledTransform() ;

StringBuilder sb = new StringBuilder();
StringWriter sw = new StringWriter(sb);

//load the Xsl
myXslTrans.Load("c:/myfile.xslt") ;

// Create and add XSLT extension
XsltArgumentList argsList = new XsltArgumentList();
myHelperObj myObj = new myHelperObj();
argsList.AddExtensionObject("urn:myObj", myObj);
myXslTrans.Transform(myXPathDoc,argsList, sw);

Then as part of your xsl stylesheet declaration add:

Whereas before this would throw an error:

By adding the XSLT extension object I could now do this: