using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Xml;
using System.Xml.Linq;
public class MainClass {
public static void Main() {
XElement firstParticipant;
XDocument xDocument = new XDocument(
new XElement("Books", firstParticipant =
new XElement("Book",
new XComment("This is a new author."),
new XAttribute("type", "Author"),
new XElement("FirstName", "J"),
new XElement("LastName", "R"))));
Console.WriteLine(xDocument);
firstParticipant.Element("FirstName").Value = "J";
firstParticipant.Nodes().OfType<XComment>().Single().Value ="LINQ";
((XElement)firstParticipant.Element("FirstName").NextNode).Nodes().OfType<XText>().Single().Value = "R";
Console.WriteLine(xDocument);
}
}