search
HomeBackend DevelopmentXML/RSS TutorialXPath syntax: Specific code introduction to using XPath examples in C#

XPath can quickly locate nodes or attributes in Xml. XPath syntax is very simple, but powerful enough. It is also the basic knowledge for using xslt.

Example


symbol




Description Example Example description are node indexes, similar to c#*







/

means starting from the root node to select



/pets



Select the root nodepet s



represents the spacer between the node and the child node



/pets/dog



Select pets dognode under

node



//xx



means searching from the entire xml document regardless of the current node position



//price



Select all pricenodes



.



A single English half-width period indicates selecting the current node



/pets/.



Select petsNode



..



Double dots indicate selecting the parent node



/pets/dog[0]/..



represents the pets node, which is the parent node of the first dog node



@xx



means selecting attributes



//dog/@color



means selecting all dog nodes colorAttribute collection



[…]



The square brackets represent the selection conditions, and the brackets are the conditions



//dog[@color ='white']



All color are white's dognodes



//dog[/price



All dognodes



and other languages The array

, array subscript starts from 1



//dog[1]


Node 1

The last

dog
Node,

last()

is the
xPath

built-in function



|

The single vertical bar represents the combination of merged nodes



//dog[@color='white'] | //cat[@color='white']



colorThe dog node with the white attribute and the catnode





The asterisk represents a node or attribute with any name



//dog/*



represents all child nodes of the dog node



//dog /@*



represents all attribute nodes of the dog node






2.

p

means Divide by, the mathematical division sign / here has been used as the separator between nodes

mod

means taking the remainder

3. XPath logical operator

=

equal to, equivalent to ==!=

in c#

is not equal to

>

is greater than

>=

is greater than or equal to

is less than is less than or equal to and

And with the relationship

or

or or relationship

4. Appropriate, it is a set of keywords plus ::double colon to indicate a node or a group of nodes related to the current node.

Use the syntax: axisname::nodetest[predicate], that is, axis name::node name[get the node condition] The specific instructions are as follows:



Keywords


Xml文件中目前節點之後的所有節點 ##Xml
Description



Example



Example description



ancestor


The parent node of the current node



ancestor::pig



The ancestor of the current node pignode


in node


ancestor-or-self



The current node and its parent node



ancestor::pig




attribute



All attributes of the current node



attribute::weight



is equivalent to @weight, attribute:: and @ are equivalent



child



all byte points of the current node



child: :*[name()!='price']



Select the child node whose name is not price



descendant



Descendant nodes



descendant::*[@*]



Descendant nodes with attributes



descendant -or-self



Descendant nodes and current node



descendant-or-self::*






#following



##following






following::*

######################## #### #######################following-sibling######################## #########目前節點的同父弟弟節點######



following-sibling::






#preceding






文件中目前節點之前的所有節點



preceding::*



######### ############################namespace################################namespace################### ######################選取目前節點的所有命名空間節點################### ####

namespace::*




parent



#目前節點的父節點



parent: :



#相當於雙點..



#preceding-sibling



###################### ###

目前節點之後的同父兄節點



preceding-sibling::*



 


self



目前節點



#self::*



#相當於單點.






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() != &#39;pig&#39;]");
               

                //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() != &#39;pig&#39;]");
                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();
        }
    }
}



The above is the detailed content of XPath syntax: Specific code introduction to using XPath examples in C#. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
如何使用C#编写时间序列预测算法如何使用C#编写时间序列预测算法Sep 19, 2023 pm 02:33 PM

如何使用C#编写时间序列预测算法时间序列预测是一种通过分析过去的数据来预测未来数据趋势的方法。它在很多领域,如金融、销售和天气预报中有广泛的应用。在本文中,我们将介绍如何使用C#编写时间序列预测算法,并附上具体的代码示例。数据准备在进行时间序列预测之前,首先需要准备好数据。一般来说,时间序列数据应该具有足够的长度,并且是按照时间顺序排列的。你可以从数据库或者

如何实现C#中的人脸识别算法如何实现C#中的人脸识别算法Sep 19, 2023 am 08:57 AM

如何实现C#中的人脸识别算法人脸识别算法是计算机视觉领域中的一个重要研究方向,它可以用于识别和验证人脸,广泛应用于安全监控、人脸支付、人脸解锁等领域。在本文中,我们将介绍如何使用C#来实现人脸识别算法,并提供具体的代码示例。实现人脸识别算法的第一步是获取图像数据。在C#中,我们可以使用EmguCV库(OpenCV的C#封装)来处理图像。首先,我们需要在项目

Redis在C#开发中的应用:如何实现高效的缓存更新Redis在C#开发中的应用:如何实现高效的缓存更新Jul 30, 2023 am 09:46 AM

Redis在C#开发中的应用:如何实现高效的缓存更新引言:在Web开发中,缓存是提高系统性能的常用手段之一。而Redis作为一款高性能的Key-Value存储系统,能够提供快速的缓存操作,为我们的应用带来了不少便利。本文将介绍如何在C#开发中使用Redis,实现高效的缓存更新。Redis的安装与配置在开始之前,我们需要先安装Redis并进行相应的配置。你可以

如何使用C#编写动态规划算法如何使用C#编写动态规划算法Sep 20, 2023 pm 04:03 PM

如何使用C#编写动态规划算法摘要:动态规划是求解最优化问题的一种常用算法,适用于多种场景。本文将介绍如何使用C#编写动态规划算法,并提供具体的代码示例。一、什么是动态规划算法动态规划(DynamicProgramming,简称DP)是一种用来求解具有重叠子问题和最优子结构性质的问题的算法思想。动态规划将问题分解成若干个子问题来求解,通过记录每个子问题的解,

如何实现C#中的遗传算法如何实现C#中的遗传算法Sep 19, 2023 pm 01:07 PM

如何在C#中实现遗传算法引言:遗传算法是一种模拟自然选择和基因遗传机制的优化算法,其主要思想是通过模拟生物进化的过程来搜索最优解。在计算机科学领域,遗传算法被广泛应用于优化问题的解决,例如机器学习、参数优化、组合优化等。本文将介绍如何在C#中实现遗传算法,并提供具体的代码示例。一、遗传算法的基本原理遗传算法通过使用编码表示解空间中的候选解,并利用选择、交叉和

如何实现C#中的图像压缩算法如何实现C#中的图像压缩算法Sep 19, 2023 pm 02:12 PM

如何实现C#中的图像压缩算法摘要:图像压缩是图像处理领域中的一个重要研究方向,本文将介绍在C#中实现图像压缩的算法,并给出相应的代码示例。引言:随着数字图像的广泛应用,图像压缩成为了图像处理中的重要环节。压缩能够减小存储空间和传输带宽,并能提高图像处理的效率。在C#语言中,我们可以通过使用各种图像压缩算法来实现对图像的压缩。本文将介绍两种常见的图像压缩算法:

如何使用C#编写背包问题算法如何使用C#编写背包问题算法Sep 19, 2023 am 09:21 AM

如何使用C#编写背包问题算法背包问题(KnapsackProblem)是一个经典的组合优化问题,它描述了一个给定容量的背包以及一系列物品,每个物品都有自己的价值和重量。目标是找到一种最佳策略,使得在不超过背包容量的情况下,装入背包的物品总价值最大。在C#中,可以通过动态规划方法来解决背包问题。具体实现如下:usingSystem;namespace

如何实现C#中的文本分类算法如何实现C#中的文本分类算法Sep 19, 2023 pm 12:58 PM

如何实现C#中的文本分类算法文本分类是一种经典的机器学习任务,它的目标是根据给定的文本数据将其分为预定义的类别。在C#中,我们可以使用一些常用的机器学习库和算法来实现文本分类。本文将介绍如何使用C#实现文本分类算法,并提供具体的代码示例。数据预处理在进行文本分类之前,我们需要对文本数据进行预处理。预处理步骤包括去除停用词(如“a”、“the”等无意义的词汇)

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
2 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. How to Fix Audio if You Can't Hear Anyone
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

EditPlus Chinese cracked version

EditPlus Chinese cracked version

Small size, syntax highlighting, does not support code prompt function

VSCode Windows 64-bit Download

VSCode Windows 64-bit Download

A free and powerful IDE editor launched by Microsoft

Dreamweaver Mac version

Dreamweaver Mac version

Visual web development tools

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

PhpStorm Mac version

PhpStorm Mac version

The latest (2018.2.1) professional PHP integrated development tool