XmlDocument和XDocument转String

1：XDocument转String直接使用ToString();XNode里面重写了ToString()方法

2：XmlDocument转String需要写代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml;
using System.Xml.Linq;
using System.IO;

namespace XmlToString
{
    class Program
    {
        static void Main(string[] args)
        {
            var xDoc = new XDocument(
                new XElement("root111",
                    new XElement("dog",
                        new XText("哈哈哈"),
                        new XAttribute("color", "black")
                        ),
                    //new XElement("cat"),
                    new XElement("pig", "pig is great")
                ));
            Console.WriteLine(xDoc.ToString());
            string strXml = "<?xml version="1.0" encoding="utf-8"?><books><book>1</book><book>2</book><book>3</book><book>4</book></books>";
            XmlDocument xx = new XmlDocument();
            xx.LoadXml(strXml);
            Console.WriteLine(xx.ToString());
            StringWriter sw = new StringWriter();
            XmlTextWriter xmlTextWriter = new XmlTextWriter(sw);
            xx.WriteTo(xmlTextWriter);
            Console.WriteLine(sw.ToString());
            Console.ReadKey();
        }
    }
}