XsltArgumentList issue with Web Services

Question

I am attempting to build a small web service to get and transform XML. To simplify, the service would have 3 main functions: public XmlDocument GetXml(string URL) - uses HttpWebRequest to get data from the URL. public XsltArgumentList Arguments(…) - Helps build argument list for the transformation if parameters or extension objects are needed. public string Transform (XmlDocument xml, XmlDocument xsl, XsltArgumentList args) - performs the transformation with an XsltCompiledTransform object and returns a string representation of the html. Once added into the site (with a WS reference) I receive an error saying "Cannot implicitly convert type 'WS.XsltArgumentList' to 'System.Xml.Xsl.XsltArgumentList' " when trying: XsltArgumentList args = [name].Arguments(); It seems to believe the XsltArgumentList is a class within the service. I tested removing the Arguments function and only adding it as a parameter to the Transform function, but it still gives the same error when I try and pass it in. If the XsltArgumentList object is created within the Transform function it works and does not show XsltArgumentList as a class within the WS reference, but I was hoping to avoid overloading the function this way. In a last ditch attempt I tried to pass the argument list as an object and convert it back in the Transform function, but receive an error saying "There was an error generating the XML document." Does anyone know why the XsltArgumentList is being referenced as a class when it's only a parameter or return type and are there any work-arounds that would enable the XsltArgumentList object to be passed as a parameter?