LINQ

            XDocument customer =
            new XDocument(
                new XDeclaration("1.0", "UTF-16", "yes"),
                new XElement("customer",
                    new XAttribute("id", "C01"),
                    new XElement("firstName", "Paolo"),
                    new XElement("lastName", "Pialorsi"),
                    new XElement("addresses",
                        new XElement("address",
                            new XAttribute("type", "email"),
                            "paolo@devleap.it"),
                    new XElement("address",
                        new XAttribute("type", "url"),
                            "http://www.devleap.it/"),
                    new XElement("address",
                        new XAttribute("type", "home"),
                            "Brescia - Italy"))));    

            //1.Declare Xdocument and have to set root node
            XDocument Content =
            new XDocument(
                new XElement("json")
            );

            //2.Add element to document
            XAttribute ID = new XAttribute("id", 1);
            XElement XmlElement = new XElement("School", ID, "南十三大学");
            Content.Root.Add(XmlElement);

Content.Descendants().Attributes().Remove();

            XmlReader reader = Content.Root.CreateReader();
            reader.MoveToContent();
            string result = reader.ReadInnerXml();