linq c#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {

            var xDoc = new XDocument(
                new XElement("root", new XElement("item", new XAttribute("color", "blak1"), new XElement("dog", new XText("dog said black is a beautiful color"), new XAttribute("color", "blak1")
                                  ), new XElement("cat"), new XElement("pig", "pig is great")
                             )
                             ,
                              new XElement("item", new XAttribute("color", "blak1"), new XElement("dog", new XText("dog said black is a beautiful color"), new XAttribute("color", "blak2")
                                  ), new XElement("cat"), new XElement("pig", "pig is great")
                             ),
                               new XElement("item", new XAttribute("color", "blak1"), new XElement("dog", new XText("dog said black is a beautiful color"), new XAttribute("color", "blak3")
                                  ), new XElement("cat"), new XElement("pag", "pig zwj is great", new XAttribute("id", "zwj"))
                             )
                             )


                );

            xDoc.Save("1.xml");
            //   Descendants 可以遍历节点下面的所有的子节点和节点  [不包括本身]
            //   Elements 只能遍历下来的子节点


            XDocument dco = XDocument.Load("a.xml");
            var temp = dco.Elements("rss").Elements("channel");
            // 用Elements 遍历
            foreach (XElement item in dco.Descendants("item"))
            {
                Console.WriteLine("标题是：{0}-{1}", item.Element("title").Value == null ? "空置" : item.Element("title").Value, item.Element("title").Name);
            }





            // 用Descendants 遍历
            foreach (XElement item in dco.Descendants("item"))
            {
                Console.WriteLine("标题是：{0}-{1}", item.Element("title").Value == null ? "空置" : item.Element("title").Value, item.Element("title").Name);
            }

            //  结合linq  查询 



            IEnumerable<XElement> xl = from item in dco.Descendants("root")

                                       where item.Attribute("color").Value == "blak1"
                                       select item;
            foreach (XElement item in xl)
            {
                Console.WriteLine(item.Element("pag").Value);
            }



            Console.WriteLine("zwj");
            Console.ReadKey();
        }
    }
}