public static void Transform(Stream xmlDoc, string sXslPath, Stream outStream)
{
    //load the Xml doc
    XPathDocument myXPathDoc = new XPathDocument(xmlDoc);

    XslTransform myXslTrans = new XslTransform();

    //load the Xsl
    myXslTrans.Load(sXslPath) ;

    //create the output stream
    using (XmlTextWriter myWriter = new XmlTextWriter(outStream, null))
    {
        //do the actual transform of Xml
        myXslTrans.Transform(myXPathDoc,null, myWriter);
    }
}