XML C#

using System;
using System.IO;
using System.Xml;
public class Sample {
  private const string filename = "sampledata.xml";
  public static void Main() {
     XmlWriterSettings settings = new XmlWriterSettings();
     settings.Indent = true;
     XmlWriter writer = XmlWriter.Create(filename, settings);
     String PItext="type=\"text/xsl\" href=\"book.xsl\"";
     writer.WriteProcessingInstruction("xml-stylesheet", PItext);
     writer.WriteDocType("book", null , null, "");
     writer.WriteComment("sample XML");
     writer.WriteStartElement("book");
     writer.WriteAttributeString("genre", "Computer");
     writer.WriteAttributeString("ISBN", "1-111111-111");
     writer.WriteElementString("title", "XML");
     writer.WriteStartElement("style");
     writer.WriteEntityRef("h");
     writer.WriteEndElement(); 
     writer.WriteElementString("price", "9.9");
     writer.WriteCData("Prices 15% off!!");
     writer.WriteEndElement();
     writer.WriteEndDocument();
     writer.Flush();
     writer.Close();  
  }
}