C# 通过XPath查询/搜索/查找XML

//实例：查找所有书名包含Harry的书

<?xml version="1.0" encoding="utf-8" ?>

<bookstore>



  <book category="COOKING">

    <title lang="en">Everyday Italian</title>

    <author>Giada De Laurentiis</author>

    <year>2005</year>

    <price>30.00</price>

  </book>



  <book category="CHILDREN">

    <title lang="en">Harry Potter</title>

    <author>J K. Rowling</author>

    <year>2005</year>

    <price>29.99</price>

  </book>



  <book category="WEB">

    <title lang="en">XQuery Kick Start</title>

    <author>James McGovern</author>

    <author>Per Bothner</author>

    <author>Kurt Cagle</author>

    <author>James Linn</author>

    <author>Vaidyanathan Nagarajan</author>

    <year>2003</year>

    <price>49.99</price>

  </book>



  <book category="WEB">

    <title lang="en">Learning XML</title>

    <author>Erik T. Ray</author>

    <year>2003</year>

    <price>39.95</price>

  </book>



</bookstore>

.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using System.Xml;
using System.Xml.XPath;

//通过XPath查询XML，在XPath中使用函数 
publicpartialclass _Default : System.Web.UI.Page 
{
    public String contx;
    protectedvoid Page_Load(object sender, EventArgs e)
    {
        contx ="";
        XPathNavigator nav;
        XPathDocument docNav;
        //XPathNodeIterator NodeIter; 
        XPathNavigator node;
        String strExpression;

        try
        {
            docNav =new XPathDocument(System.AppDomain.CurrentDomain.BaseDirectory +"bookdemo.xml");
            nav = docNav.CreateNavigator();
            strExpression ="/bookstore/book[contains(title/text(), 'Harry')]/title";
            node = nav.SelectSingleNode(strExpression);
            contx += node.InnerXml;

            /*
            NodeIter = nav.Select(strExpression);
            while (NodeIter.MoveNext())
            {
                contx += NodeIter.Current.Value + "<br />";
            }
            */
        }
        catch (Exception)
        {
            contx ="Unfind !";
        }
    }
}

(注释部分为查询全部节点的方法)