c#通过xpath读取xml示例

需要修改main方法第一行代码的路径为你的books.xml文件绝对路径或相对路径。代码演示了xpath各种语法的使用情况

books.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<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>

主程序

using system;
using system.collections.generic;
using system.linq;
using system.text;
using system.threading.tasks;
using system.xml;

namespace xmlprocesstest
{
    public class program
    {
        /// <summary>
        /// 加载xml文件
        /// </summary>
        /// <param name="xmlfilepath">xml文件路径</param>
        /// <returns></returns>
        public static xmldocument loadxmldoc(string xmlfilepath)
        {
            var xmldoc = new xmldocument();
            xmldoc.load(xmlfilepath);

            return xmldoc;
        }

        /// <summary>
        /// 根据指定的xpath表达式获取xml结点列表
        /// </summary>
        /// <param name="xmldoc"></param>
        /// <param name="xpathexpr"></param>
        /// <returns></returns>
        public static xmlnodelist getxmlnodes(xmldocument xmldoc, string xpathexpr)
        {
            if (xmldoc == null)
                return null;

            return xmldoc.selectnodes(xpathexpr);
        }

        public static string getxmlnodeinfo(xmlnode node, string type="xml")
        {
            if (node == null)
                return "empty node or error node";

            string xmlnodeinfo = null;
            switch (type)
            {
                case "text":
                    xmlnodeinfo = node.innertext;
                    break;
                default:
                    xmlnodeinfo = node.innerxml;
                    break;
            }

            return xmlnodeinfo;
        }

        public static void main(string[] args)
        {
            var xmldoc = loadxmldoc(@"你的books.xml文件路径");

            var rootexpr = "/bookstore";   //  根节点对应的xpath表达式
            var rootnode = getxmlnodes(xmldoc, rootexpr);   //
            console.writeline("xpath表达式为 /bookstore，根节点bookstore的所有子节点xml内容如下：");
            console.writeline(getxmlnodeinfo(rootnode[0]));

            console.writeline();

            var allbooksexpr = "/bookstore/book"; // 根节点bookstore的子元素的所有子节点
            var booknodes = getxmlnodes(xmldoc, allbooksexpr);
            console.writeline("xpath表达式为 bookstore/book，book节点共有：" + booknodes.count);

            console.writeline();

            var anybookexpr = "//book"; // 选取所有book子元素，而不管它们在文档中的位置
            var anybooknodes = getxmlnodes(xmldoc, anybookexpr);
            console.writeline("xpath表达式为 //book，book节点共有：" + anybooknodes.count);
            console.writeline(anybooknodes[0].innerxml);
            console.writeline(anybooknodes[0].outerxml);

            console.writeline();

            var categoryexpr = "//@category";   // 选取名为category的所有属性
            var allcategorynodes = getxmlnodes(xmldoc, categoryexpr);
            console.writeline("xpath表达式为 //@category，category节点共有：" + allcategorynodes.count);
            console.writeline(allcategorynodes[0].innertext);
            console.writeline(allcategorynodes[0].innerxml);

            console.writeline();

            var titlewithlangexpr = "//title[@lang]";   // 选取所有带有lang属性的title节点
            var titlewithlangnodes = getxmlnodes(xmldoc, titlewithlangexpr);
            console.writeline("xpath表达式为 //title[@lang]，带lang属性的title节点共有：" + titlewithlangnodes.count);
            console.writeline(getxmlnodeinfo(titlewithlangnodes[0]));

            var englishtitleexpr = "//title[@lang='en']";   // 选取所有lang属性值为en的title节点
            var englishtitlenodes = getxmlnodes(xmldoc, englishtitleexpr);
            console.writeline("xpath表达式为 //title[@lang='en']，lang属性值为en的title节点共有：" + englishtitlenodes.count);
            console.writeline(getxmlnodeinfo(englishtitlenodes[0]));

            console.writeline();

            // 使用索引的xpath查询
            var indexexpr = "/bookstore/book[1]";   // 取bookstore子元素的第一个book元素
            var firstbooknode = getxmlnodes(xmldoc, indexexpr);
            console.writeline("xpath表达式为 /bookstore/book[1]，节点数为：" + firstbooknode.count);
            console.writeline(getxmlnodeinfo(firstbooknode[0]));

            console.writeline();

            var indexexpr2 = "/bookstore/book[last()]"; // 取bookstore子元素的最后一个book元素
            var lastbooknode = getxmlnodes(xmldoc, indexexpr2);
            console.writeline("xpath表达式为 /bookstore/book[last()]，节点数为：" + lastbooknode.count);
            console.writeline(getxmlnodeinfo(lastbooknode[0]));

            console.writeline();

            var indexexpr3 = "/bookstore/book[last()-1]"; // 取bookstore子元素的倒数第二个book元素
            var nextbylastbooknode = getxmlnodes(xmldoc, indexexpr3);
            console.writeline("xpath表达式为 /bookstore/book[last()-1]，节点数为：" + lastbooknode.count);
            console.writeline(getxmlnodeinfo(nextbylastbooknode[0]));

            console.writeline();

            var indexexpr4 = "/bookstore/book[position()<3]"; // 取bookstore的前两个book子元素
            var firsttwobooknodes = getxmlnodes(xmldoc, indexexpr4);
            console.writeline("xpath表达式为 /bookstore/book[position()<3]，节点数为：" + firsttwobooknodes.count);
            console.writeline(getxmlnodeinfo(firsttwobooknodes[0]));

            console.writeline();

            // 带属性值过滤条件的xpath表达式
            var fileterexpr = "/bookstore/book[price>35.00]";   // 选取bookstore的所有price属性值大于35.00的book元素
            var bookgt35nodes = getxmlnodes(xmldoc, fileterexpr);
            console.writeline("xpath表达式为 /bookstore/book[price>35.00]，节点数为：" + bookgt35nodes.count);
            console.writeline(getxmlnodeinfo(bookgt35nodes[0]));

            // 通配符
            // @*                匹配任何属性节点
            // node()             匹配任何类型的节点
            // /bookstore/*   选取 bookstore 元素的所有子元素
            // //*                   选取文档的所有元素
            // //title[@*]        选取所有带有属性的 title 元素
            var alltitlewithattrexpr = "//title[@*]";
            var alltitlewithattrnodes = getxmlnodes(xmldoc, alltitlewithattrexpr);
            console.writeline("xpath表达式为 title[@*]，节点数为：" + alltitlewithattrnodes.count);
            console.writeline(getxmlnodeinfo(alltitlewithattrnodes[0]));

            console.writeline();

            // |        或
            var titleandpriceexpr = "//book/title | //book/price";
            var titleandpricenodes = getxmlnodes(xmldoc, titleandpriceexpr);
            console.writeline("xpath表达式为 //book/title | //book/price，节点数为：" + titleandpricenodes.count);
            console.writeline(getxmlnodeinfo(titleandpricenodes[0]));

            // text()  选取文本
            var titletextexpr = "//title/text()";
            var titletextnodes = getxmlnodes(xmldoc, titletextexpr);
            console.writeline("xpath表达式为 //title/text()，节点数为：" + titletextnodes.count);
            console.writeline(titletextnodes[0].value); // 文本节点的值

            console.readkey();
        }
    }
}