ASP.NET 2.0 :

            XslCompiledTransform transformer = new XslCompiledTransform();

            transformer.Load(Server.MapPath("XSLTCreator.xsl"), XsltSettings.TrustedXslt, new XmlUrlResolver());

            XsltArgumentList args = new XsltArgumentList();
            args.AddParam("style", "", "template/style.css");

            transformer.Transform(new XPathDocument(Server.MapPath("XSLTCreator.xml")), args, output);

ASP.NET 1.1 :
            

            XmlDocument XmlDoc=new XmlDocument();
            XmlDoc.Load(strFilePath);
 
            XslTransform xslt = new XslTransform();
            xslt.Load(strXslPath);
 
            XsltArgumentList xslArg = new XsltArgumentList();
            xslArg.AddParam("Key1", "",IXPath);
            xslArg.AddParam("Path", "",strPath);

            xslt.Transform(XmlDoc,xslArg,writer,null);

至于到XSLT怎么拿就不说了，自己起个变量获取吧。