Traverse Down from an XElement Object via the Descendants Method in CSharp

using System;//from  w  ww .j  a v a2 s .  c  o  m
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 XDeclaration("1.0", "UTF-8", "yes"),
      new XDocumentType("Books", null, "Books.dtd", null),
      new XProcessingInstruction("Book", "out-of-print"),
      new XElement("Books", firstParticipant =
      new XElement("Book",
      new XComment("a new author."),
      new XProcessingInstruction("AuthorHandler", "new"),
      new XAttribute("type", "Author"),
        new XElement("FirstName",
       new XText("A"),
       new XElement("NickName", "J")),
        new XElement("LastName", "R")),
         new XElement("Book",
        new XAttribute("type", "Author"),
        new XElement("FirstName", "E"),
        new XElement("LastName", "B"))));

        foreach (XElement element in firstParticipant.Descendants()) {
            Console.WriteLine(element.Name);
        }

    }
}