XsltArgumentList doesn't accept long parameter values

I have problems passing parameters from C# application to XSL file and doing a transformation. My code is below.: XsltArgumentList xslArg = new XsltArgumentList(); String key = "grandpa/father/son"; // This is the name of node I want pass and gets it value xslArg.AddParam("xslParam", "", key); // Create the XslTransform and load the stylesheet. XslTransform xslt = new XslTransform(); xslt.Load(stylesheet); // xsl stylesheet XmlUrlResolver xmlUrlResolver = new XmlUrlResolver(); // Output to console. XmlTextWriter writer = new XmlTextWriter(Console.Out); // Transform the xml file xslt.Transform(new XPathDocument(filename), xslArg, writer, xmlUrlResolver); writer.Close(); ---------------- XSL file looks like this The problem is that node grandpa/father/son is not executed! It's passed to XSL file but XslTransform classes transsform method does not fetch it's value from xml file. It only shows the key value in console. Node grandpa/father/son has value in it's xml file. So, am I missing something or is there a bug in XsltArgumentList and it's transformation. Has anyone any ideas what could be wrong? Cheers!