using System;

using System.IO;

using System.Xml;

public class Sample

{

  public static void Main()

  {

      XmlDocument doc = new XmlDocument();

      doc.Load("newbooks.xml");

      // Create an XmlNamespaceManager to resolve the default namespace.

      XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);

      nsmgr.AddNamespace("bk", "urn:newbooks-schema");

      // Select the first book written by an author whose last name is Atwood.

      XmlNode book;

      XmlElement root = doc.DocumentElement;

     book = root.SelectSingleNode("descendant::bk:book[bk:author/bk:last-name='Atwood']", nsmgr);

      Console.WriteLine(book.OuterXml);

  }

}

<?xml version='1.0'?>

<bookstore xmlns="urn:newbooks-schema">

  <book genre="novel" style="hardcover">

    <title>The Handmaid's Tale</title>

    <author>

      <first-name>Margaret</first-name>

      <last-name>Atwood</last-name>

    </author>

    <price>19.95</price>

  </book>

  <book genre="novel" style="other">

    <title>The Poisonwood Bible</title>

    <author>

      <first-name>Barbara</first-name>

      <last-name>Kingsolver</last-name>

    </author>

    <price>11.99</price>

  </book>

</bookstore>