XML C#

using System;
using System.IO;
using System.Xml;
public class Sample {
  public static void Main() {
     XmlWriter writer = null;
     writer = XmlWriter.Create("sampledata.xml");
     writer.WriteStartElement("book");
     writer.WriteAttributeString("xmlns","bk", null,"urn:book");
     writer.WriteAttributeString("ISBN", "urn:book", "1-111-111");
     writer.WriteElementString("price", "1.5");
     writer.WriteEndElement();
     writer.Flush();
     writer.Close();  
  }
}