<?xml version="1.0" encoding="UTF-8"?>
<books>
<book>
  <name>哈里波特</name>
  <price>10</price>
  <memo>这是一本很好看的书。</memo>
</book>
<book id="B02">
  <name>三国演义</name>
  <price>10</price>
  <memo>四大名著之一。</memo>
</book>
<book id="B03">
  <name>水浒</name>
  <price>6</price>
  <memo>四大名著之一。</memo>
</book>
<book id="B04">
  <name>红楼</name>
  <price>5</price>
  <memo>四大名著之一。</memo>
</book>
</books>  

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

namespace TestXml
{
    class Program
    {
        static void Main(string[] args)
        {
             XmlElement theBook = null, theElem = null, root = null;
            XmlDocument xmldoc = new XmlDocument();
            try
            {
                 xmldoc.Load("Books.xml");
                 root = xmldoc.DocumentElement;

                //---   新建一本书开始 ----
                 theBook = xmldoc.CreateElement("book");
                 theElem = xmldoc.CreateElement("name");
                 theElem.InnerText = "新书";
                 theBook.AppendChild(theElem);

                 theElem = xmldoc.CreateElement("price");
                 theElem.InnerText = "20";
                 theBook.AppendChild(theElem);

                 theElem = xmldoc.CreateElement("memo");
                 theElem.InnerText = "新书更好看。";
                 theBook.AppendChild(theElem);
                 root.AppendChild(theBook);
                 Console.Out.WriteLine("---   新建一本书开始 ----");
                 Console.Out.WriteLine(root.OuterXml);
                //---   新建一本书完成 ----

                //---   下面对《哈里波特》做一些修改。 ----
                //---   查询找《哈里波特》----
                 theBook = (XmlElement)root.SelectSingleNode("/books/book[name='哈里波特']");
                 Console.Out.WriteLine("---   查找《哈里波特》 ----");
                 Console.Out.WriteLine(theBook.OuterXml);
                //---   此时修改这本书的价格 -----
                 theBook.GetElementsByTagName("price").Item(0).InnerText = "15";//getElementsByTagName返回的是NodeList，所以要跟上item(0)。另外，GetElementsByTagName("price")相当于SelectNodes(".//price")。
                 Console.Out.WriteLine("---   此时修改这本书的价格 ----");
                 Console.Out.WriteLine(theBook.OuterXml);
                //---   另外还想加一个属性id，值为B01 ----
                 theBook.SetAttribute("id", "B01");
                 Console.Out.WriteLine("---   另外还想加一个属性id，值为B01 ----");
                 Console.Out.WriteLine(theBook.OuterXml);
                //---   对《哈里波特》修改完成。 ----

                //---   再将所有价格低于10的书删除   ----
                 theBook = (XmlElement)root.SelectSingleNode("/books/book[@id='B02']");
                 Console.Out.WriteLine("---   要用id属性删除《三国演义》这本书 ----");
                 Console.Out.WriteLine(theBook.OuterXml);
                 theBook.ParentNode.RemoveChild(theBook);
                 Console.Out.WriteLine("---   删除后的ＸＭＬ ----");
                 Console.Out.WriteLine(xmldoc.OuterXml);

                //---   再将所有价格低于10的书删除   ----
                 XmlNodeList someBooks = root.SelectNodes("/books/book[price<10]");
                 Console.Out.WriteLine("---   再将所有价格低于10的书删除   ---");
                 Console.Out.WriteLine("---   符合条件的书有　" + someBooks.Count + "本。   ---");

                for (int i = 0; i < someBooks.Count; i++)
                {
                     someBooks.Item(i).ParentNode.RemoveChild(someBooks.Item(i));
                 }
                 Console.Out.WriteLine("---   删除后的ＸＭＬ ----");
                 Console.Out.WriteLine(xmldoc.OuterXml);

                 xmldoc.Save("books.xml");//保存到books.xml

                 Console.In.Read();
             }
            catch (Exception e)
            {
                 Console.Out.WriteLine(e.Message);
             }
         }
     }
}