Dynamic crm 2011 FetchXML results into XmlTextReader to build an XML output

Hi I have got a little problem here to convert FetchXML web service response into an XML file out put.

1. Retrieving FetchXml EntityCollection

 EntityCollection result = _orgService.RetrieveMultiple(new FetchExpression(fetchXml));

2. then Needed to convert it into XML file

  a) Put into

  XmlTextReader reader = new XmlTextReader(result, XmlNodeType.Document, null);

 Problem: FetchXML result needed to have a string to put into the parameter above.

 b) get a string Builder StringBuilder mysb1 = new StringBuilder();

c) Loop through and build into XML file

mysb1.Append(@"<?xml version='1.0' standalone='yes' ?>");
                while (reader.Read())
                {
                    switch (reader.NodeType)
                    {
                        case XmlNodeType.Element:
                            mysb1.Append("<" + reader.Name + ">");
                            break;
                        case XmlNodeType.Text:
                            mysb1.Append(reader.Value);
                            break;
                        case XmlNodeType.EndElement:
                            mysb1.Append("</" + reader.Name + ">");
                            break;
                    }
                }

Any help would be appreciated. Thanks.