c# - Return XML document with REST API -

i return xml document rest api request:

[httppost] public string getclassxml(httprequestmessage req) {      var response = request.createresponse(httpstatuscode.ok);      var serializer = new system.web.script.serialization.javascriptserializer();      classxml classid = new classxml();      xmldocument doc = new xmldocument();       try      {          var data = req.content.readasstringasync().result;          classid = serializer.deserialize<classxml>(data.tostring().trim());      }      catch (exception ex)      {           throw new exception(ex.message);      }       string path = asdb.readvalue("select definitionxml alclass classid='" + classid.classid + "'").tostring();       xmltextreader reader = new xmltextreader(appdomain.currentdomain.basedirectory + "resource\\" + percorso);      reader.read();      doc.load(reader);       return doc.innerxml; } 

but in way string, have xmldocument not string. tried return xmldocument doc, gives me error: 'objectcontent`1' type failed serialize response body content type 'application/xml; charset=utf-8'. have ideas?

as wrote here few seconds ago (but deleted answer) problem xmldocument not serializable, if use xmlelement instead ok. here did:

[httppost] public xmlelement getclassxml(httprequestmessage req) {     var response = request.createresponse(httpstatuscode.ok);     var serializer = new system.web.script.serialization.javascriptserializer();     classxml classid = new classxml();     xmldocument doc = new xmldocument();      try     {         var data = req.content.readasstringasync().result;         classid = serializer.deserialize<classxml>(data.tostring().trim());     }     catch (exception ex)     {          throw new exception(ex.message);     }      string path = asdb.readvalue("select definitionxml alclass classid='" + classid.classid + "'").tostring();       xmltextreader reader = new xmltextreader(appdomain.currentdomain.basedirectory + "resource\\" + percorso);      reader.read();      doc.load(reader);      xmlelement element = doc.documentelement;       return element; }