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(){
            
      XmlDocument document = new XmlDocument();
      document.Load("domainBooks.xml");
      XPathNavigator navigator = document.CreateNavigator();
      
      navigator.MoveToChild("bookstore", "http://www.domain.com/books");
      navigator.MoveToChild("book", "http://www.domain.com/books");
      
      navigator.PrependChildElement(navigator.Prefix, "pages", navigator.LookupNamespace(navigator.Prefix), "100");
      
      Console.WriteLine(navigator.OuterXml);
   }
}