C#中使用XPath的XPathNavigator类移动选择XML数据

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XPathNavigator类包含移动和选择XML所需元素的所有方法。
1.创建：
a.如果是从XPathDocument中创建，则是只读的，只能浏览数据；
b.如果是从XmlDocument中创建，则可以编辑文档；
2.查询：使用Select()方法通过XPath语句查询；
3.迭代：使用XPathNodeIterator类，MoveNext()方法移动下一个节点；Current属性表示当前节点；
4.求值：使用Evaluate()方法计算表达式的值；
5.插入节点：先检查CanEdit属性是否为true，再使用InsertAfter()方法插入新节点。

实例：查询和编辑books.xml

using System;
using System.Collections.Generic;
using System.Text;
using System.Xml.XPath;
using System.Xml;
 
namespace Magci.Test.XML.TestXPath
{
    class Program
    {
        private static XPathDocument doc;
        private static XPathNavigator nav;
 
        static void Main(string[] args)
        {
            doc = new XPathDocument(@"../../books.xml");
            nav = ((IXPathNavigable)doc).CreateNavigator();
            SearchByGenre("nove");
            TotalPrice();
            Insert();
            Console.ReadLine();
        }
 
        public static void SearchByGenre(string search)
        {
            //查询bookstore的子元素book中genre属性值为novel的所有节点
            XPathNodeIterator iter = nav.Select("/bookstore/book[@genre='" + search + "l']");
 
            Console.WriteLine("/nSearchByGenre:/n");
            while (iter.MoveNext())
            {
                //迭代所有子代节点
                XPathNodeIterator newIter = iter.Current.SelectDescendants(XPathNodeType.Element, false);
                while (newIter.MoveNext())
                {
                    Console.WriteLine(newIter.Current.Name + " : " + newIter.Current.Value);
                }
            }
        }
 
        public static void TotalPrice()
        {
            XPathNodeIterator iter = nav.Select("/bookstore/book");
            Console.WriteLine("/nTotalPrice:/n");
            while (iter.MoveNext())
            {
                XPathNodeIterator newIter = iter.Current.SelectDescendants(XPathNodeType.Element, false);
                while (newIter.MoveNext())
                {
                    if (newIter.Current.Name == "price")
                    {
                        Console.WriteLine(newIter.Current.Name + " : " + newIter.Current.Value);
                    }
                }
            }
            //统计图书总价
            Console.WriteLine("Total price = {0}", nav.Evaluate("sum(bookstore/book/price)"));
        }
 
        //插入节点
        public static void Insert()
        {
            XmlDocument doc = new XmlDocument();
            doc.Load(@"../../books.xml");
            XPathNavigator nav2 = doc.CreateNavigator();
            //判断是否可编辑
            if (nav2.CanEdit)
            {
                XPathNodeIterator iter = nav2.Select("bookstore/book/price");
                while (iter.MoveNext())
                {
                    //在当前节点之后插入新节点
                    iter.Current.InsertAfter("<disc>5</disc>");
                }
            }
            doc.Save(@"../../newBooks.xml");
            Console.WriteLine("/nnewBooks.xml saved successful./n");
        }
    }
}



book.xml:


<?xml version="1.0" encoding="utf-8" ?>
<bookstore>
  <book genre="autobiography" publicationdate="1991" ISBN="1-861003-11-0">
    <title>The Autobiography of Benjamin Franklin</title>
    <author>
      <first-name>Benjamin</first-name>
      <last-name>Franklin</last-name>
    </author>
    <price>8.99</price>
  </book>
  <book genre="novel" publicationdate="1967" ISBN="0-201-63361-2">
    <title>The Confidence Man</title>
    <author>
      <first-name>Herman</first-name>
      <last-name>Melville</last-name>
    </author>
    <price>11.99</price>
  </book>
  <book genre="philosophy" publicationdate="1991" ISBN="1-861001-57-6">
    <title>The Gorgias</title>
    <author>
      <name>Plato</name>
    </author>
    <price>9.99</price>
  </book>
</bookstore>


newBooks.xml:编辑后的文档



<?xml version="1.0" encoding="utf-8"?>
<bookstore>
  <book genre="autobiography" publicationdate="1991" ISBN="1-861003-11-0">
    <title>The Autobiography of Benjamin Franklin</title>
    <author>
      <first-name>Benjamin</first-name>
      <last-name>Franklin</last-name>
    </author>
    <price>8.99</price>
    <disc>5</disc>
  </book>
  <book genre="novel" publicationdate="1967" ISBN="0-201-63361-2">
    <title>The Confidence Man</title>
    <author>
      <first-name>Herman</first-name>
      <last-name>Melville</last-name>
    </author>
    <price>11.99</price>
    <disc>5</disc>
  </book>
  <book genre="philosophy" publicationdate="1991" ISBN="1-861001-57-6">
    <title>The Gorgias</title>
    <author>
      <name>Plato</name>
    </author>
    <price>9.99</price>
    <disc>5</disc>
  </book>
</bookstore>