Get Descendants Elements with where clause in CSharp

using System;/*  w  ww .  j  a va  2s . 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() {
        XDocument xDocument = new XDocument(
          new XElement("Books",
            new XElement("Book",
              new XAttribute("type", "Author"),
              new XElement("FirstName", "A"),
              new XElement("LastName", "B")),

          new XElement("Book",
            new XAttribute("type", "Author"),
            new XElement("FirstName", "C"),
            new XElement("LastName", "D"))));

        IEnumerable<XElement> elements = xDocument.Descendants("Book")
           .Where(e => ((string)e.Element("FirstName")) == "C");
        foreach (XElement element in elements) {
            Console.WriteLine("Element: {0} : value = {1}",element.Name, element.Value);
        }
    }
}