using System;

using System.Text;

using System.Linq;

using System.Xml;

using System.Xml.Linq;

​

public class Program

{

       public static void Main(string[] args)

       {

           XNamespace ns = "http://tempuri.org/NBAppSchema.xsd";

           // option 1

           var doc = new XDocument(new XElement("root", new XAttribute("attr1", "val1"), new XElement("SubNode")));

           Console.WriteLine(doc.ToString());

           doc.Root.Add(new XAttribute(XNamespace.Xmlns + "ns", ns));

           doc.Root.Add(new XElement(ns+"NSSubNode", new XAttribute("attr2", "val2")));

           Console.WriteLine(doc.ToString());

           Console.WriteLine();

           // option 2

           var doc2 = new XDocument(new XElement(ns + "root", new XAttribute("attr1", "val1"), new XElement(ns + "SubNode")));

           Console.WriteLine(doc2.ToString());

​

       }

​

}