XPATH

Xpath 匹配节点的内容为空（inner text 为空）

分类： XML .net 2011-02-17 11:18 695人阅读 评论(0) 收藏 举报

stringnullencodingexceptionxmlbooks

需求是从以下写出能从下面的xml中取出Title内容（inner text）为空的节点的XPath： 

<?xml version="1.0" encoding="utf-8" ?>
<BookCatalog>
<Books>
<Book>
<Title>Asp.net</Title>
<Price>22.5</Price>
<Author>Abraham</Author>
</Book>
<Book>
<Title></Title>
<Price>22.5</Price>
<Author>Abraham</Author>
</Book>
</Books>
</BookCatalog>

<?xml version="1.0" encoding="utf-8" ?>
<BookCatalog>
<Books>
<Book>
<Title>Asp.net</Title>
<Price>22.5</Price>
<Author>Abraham</Author>
</Book>
<Book>
<Title></Title>
<Price>22.5</Price>
<Author>Abraham</Author>
</Book>
</Books>
</BookCatalog>

容易写出错误的xPath有:

//Book[Title[text()='']]

//Book[Title[text() is null]]

//Book[Title[node() is null]]

//Book[Title[. is null]]

//Book[Title[text()=]]

//Book[Title[text()='']] 

//Book[Title[text() is null]] 

//Book[Title[node() is null]] 

//Book[Title[. is null]] 

//Book[Title[text()=]] 

正确的写法为：

//Book[Title[not(text())]] 或

//Book[Title[not(node())]]

//Book[Title[not(text())]] 或  

//Book[Title[not(node())]]

验证程序为：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
namespace TestXPath
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] errorXPaths = { "//Book[Title[text()='']]",
                "//Book[Title[text() is null]]",
                "//Book[Title[node() is null]]",
                "//Book[Title[. is null]]",
                "//Book[Title[text()=]]"};
            string[] correctXPaths = { "//Book[Title[not(text())]]", "//Book[Title[not(node())]]" };
            string xml = "<?xml version=\"1.0\" encoding=\"utf-8\" ?> " + @"
                        <BookCatalog>
                        <Books>
                        <Book>
                        <Title>Asp.net</Title>
                        <Price>22.5</Price>
                        <Author>Abraham</Author>
                        </Book>
                        <Book>
                        <Title></Title>
                        <Price>22.5</Price>
                        <Author>Abraham</Author>
                        </Book>
                        </Books>
                        </BookCatalog>";
            XmlDocument xmlDocument = new XmlDocument();
            xmlDocument.LoadXml(xml);
            foreach (string errorxPath in errorXPaths)
            {
                try
                {
                    XmlNodeList nodeList = xmlDocument.SelectNodes(errorxPath);
                    Console.WriteLine("errorxPath:" + errorxPath);
                    Console.WriteLine("nodeList.Count:" + nodeList.Count);
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.Message);
                }
            }

            foreach (string correctXPath in correctXPaths)
            {
                XmlNodeList nodeList = xmlDocument.SelectNodes(correctXPath);
                Console.WriteLine("correctXPath:" + correctXPath);
                Console.WriteLine("nodeList.Count:" + nodeList.Count);
            }

            Console.Read();
        }
    }
}