XML C#

using System;
using System.Linq;
using System.Xml;
using System.Xml.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Xml.XPath;
public class MainClass{
   public static void Main(){
            
          XPathDocument document = new XPathDocument("books.xml");
          XPathNavigator navigator = document.CreateNavigator();
          Hashtable table = new Hashtable(XPathNavigator.NavigatorComparer);
          
          // Add nodes to the Hashtable.
          foreach (XPathNavigator navigator2 in navigator.Select("//book"))
          {
              object value = navigator2.Evaluate("string(./title)");
              table.Add(navigator2.Clone(), value);
              Console.WriteLine("Added book with title {0}", value);
          }
          
          Console.WriteLine(table.Count);
          Console.WriteLine("Does the Hashtable have the book \"XML\"?");
          Console.WriteLine(table.Contains(navigator.SelectSingleNode("//book[title='XML']")));
   }
}