[转载]XPath语法 在C#中使用XPath示例

[转载]XPath语法 在C#中使用XPath示例 – 玉开 – 博客园.

XPath可以快速定位到Xml中的节点或者属性。XPath语法很简单，但是强大够用，它也是使用xslt的基础知识。

示例Xml：

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

100     this is a black cat

80     this is a white cat

80     this is a yellow cat

100     this is a black dog

80     this is a white dog

80     this is a yellow dog

XPath的语法：

1. XPath中的符号

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

namespace UseXPathDotNet
{
class Program
{
static void Main(string[] args)
{
UseXPathWithXPathDocument();

UseXPathWithXmlDocument();

Console.Read();
}

static void UseXPathWithXmlDocument()
{
XmlDocument doc = new XmlDocument();
doc.Load("http://www.cnblogs.com/yukaizhao/rss");
//使用xPath选择需要的节点
XmlNodeList nodes = doc.SelectNodes("/rss/channel/item[position()<=10]");
foreach (XmlNode item in nodes)
{
string title = item.SelectSingleNode("title").InnerText;
string url = item.SelectSingleNode("link").InnerText;
Console.WriteLine("{0} = {1}", title, url);
}
}

static void UseXPathWithXPathDocument()
{
XPathDocument doc = new XPathDocument("http://www.cnblogs.com/yukaizhao/rss");
XPathNavigator xPathNav = doc.CreateNavigator();
//使用xPath取rss中最新的10条随笔
XPathNodeIterator nodeIterator = xPathNav.Select("/rss/channel/item[position()<=10]");
while (nodeIterator.MoveNext())
{
XPathNavigator itemNav = nodeIterator.Current;
string title = itemNav.SelectSingleNode("title").Value;
string url = itemNav.SelectSingleNode("link").Value;
Console.WriteLine("{0} = {1}",title,url);
}

}
}
}

XPath使用示例，请看下面的代码注释

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

namespace UseXPath1
{
class Program
{
static void Main(string[] args)
{
string xml = @"<!--?xml version=""1.0"" encoding=""utf-8"" ?-->

100     this is a black cat

80     this is a white cat

110     this is a yellow cat

114     this is a black dog

80     this is a white dog

80     this is a yellow dog

8000     this is a white pig
";

using (StringReader rdr = new StringReader(xml))
{
XmlDocument doc = new XmlDocument();
doc.Load(rdr);

//取所有pets节点下的dog字节点
XmlNodeList nodeListAllDog = doc.SelectNodes("/pets/dog");

//所有的price节点
XmlNodeList allPriceNodes = doc.SelectNodes("//price");

//取最后一个price节点
XmlNode lastPriceNode = doc.SelectSingleNode("//price[last()]");

//用双点号取price节点的父节点
XmlNode lastPriceParentNode = lastPriceNode.SelectSingleNode("..");

//选择weight*count=40的所有动物，使用通配符*
XmlNodeList nodeList = doc.SelectNodes("/pets/*[@weight*@count=40]");

//选择除了pig之外的所有动物,使用name()函数返回节点名字
XmlNodeList animalsExceptPigNodes = doc.SelectNodes("/pets/*[name() != 'pig']");

//选择价格大于100而不是pig的动物
XmlNodeList priceGreaterThan100s = doc.SelectNodes("/pets/*[price div @weight &gt;10 and name() != 'pig']");
foreach (XmlNode item in priceGreaterThan100s)
{
Console.WriteLine(item.OuterXml);
}

//选择第二个dog节点
XmlNode theSecondDogNode = doc.SelectSingleNode("//dog[position() = 2]");

//使用xpath ，axes 的 parent 取父节点
XmlNode parentNode = theSecondDogNode.SelectSingleNode("parent::*");

//使用xPath选择第二个dog节点前面的所有dog节点
XmlNodeList dogPresibling = theSecondDogNode.SelectNodes("preceding::dog");

//取文档的所有子孙节点price
XmlNodeList childrenNodes = doc.SelectNodes("descendant::price");
}

Console.Read();
}
}
}

C#处理Xml的相关随笔：