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apprentissage XML (6) dans l'instance c#Xpath
- 黄舟original
- 2017-02-23 14:37:401480parcourir
Réimpression : http://www.php.cn/
En c#, nous recherchons et parcourons souvent des nœuds, c'est ce que nous pouvons utiliser XPath syntaxe, Exemple 🎜>
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symbole <?xml version="1.0" encoding="utf-8" ?> <pets> <cat color="black" weight="10"> <price>100</price> <desc>this is a black cat</desc> </cat> <cat color="white" weight="9"> <price>80</price> <desc>this is a white cat</desc> </cat> <cat color="yellow" weight="15"> <price>80</price> <desc>this is a yellow cat</desc> </cat> <dog color="black" weight="10"> <price>100</price> <desc>this is a black dog</desc> </dog> <dog color="white" weight="9"> <price>80</price> <desc>this is a white dog</desc> </dog> <dog color="yellow" weight="15"> <price>80</price> <desc>this is a yellow dog</desc> </dog> </pets> |
Description |
Exemple |
Exemple de description
5. 常用的XPath函数介绍： 在XPath表达式中常用的函数有下面两个： position() 表示节点的序号例如 //cat[position() = 2] 表示取序号为2的dog节点 last() 表示取最后一个节点 //cat[last()] name() 表示当前节点名字 /pets/*[name() != 'pig'] 表示/pets下名字不是pig的子节点
XPath的函数还有很多，包括字符串函数，数字函数和时间函数等，具体可以参考w3的网站。
以上是XPath的语法，下面我们看下如何在.Net中使用XPath 在.Net中可以通过XPathDocument或者XmlDocument类使用XPath。XPathDocument是只读的方式定位Xml节点或者属性文本等，而XmlDocument则是可读写的。
如下代码示例展示了如何使用XPathDocument和XmlDocument。 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"" ?>
<pets>
<cat color=""black"" weight=""10"" count=""4"">
<price>100</price>
<desc>this is a black cat</desc>
</cat>
<cat color=""white"" weight=""9"" count=""5"">
<price>80</price>
<desc>this is a white cat</desc>
</cat>
<cat color=""yellow"" weight=""15"" count=""1"">
<price>110</price>
<desc>this is a yellow cat</desc>
</cat>
<dog color=""black"" weight=""10"" count=""7"">
<price>114</price>
<desc>this is a black dog</desc>
</dog>
<dog color=""white"" weight=""9"" count=""4"">
<price>80</price>
<desc>this is a white dog</desc>
</dog>
<dog color=""yellow"" weight=""15"" count=""15"">
<price>80</price>
<desc>this is a yellow dog</desc>
</dog>
<pig color=""white"" weight=""100"" count=""2"">
<price>8000</price>
<desc>this is a white pig</desc>
</pig>
</pets>";
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 p @weight >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();
}
}
}以上就是xml学习（6） 在c#Xpath实例的内容，更多相关内容请关注PHP中文网（www.php.cn）！ |