C#中使用XPath的XPathNavigator类移动选择XML数据
XPathNavigator类包含移动和选择XML所需元素的所有方法。
1.创建：
a.如果是从XPathDocument中创建，则是只读的，只能浏览数据；
b.如果是从XmlDocument中创建，则可以编辑文档；
2.查询：使用Select()方法通过XPath语句查询；
3.迭代：使用XPathNodeIterator类，MoveNext()方法移动下一个节点；Current属性表示当前节点；
4.求值：使用Evaluate()方法计算表达式的值；
5.插入节点：先检查CanEdit属性是否为true，再使用InsertAfter()方法插入新节点。
实例：查询和编辑books.xml
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using System;
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using System.Collections.Generic;
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using System.Text;
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using System.Xml.XPath;
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using System.Xml;
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namespace Magci.Test.XML.TestXPath
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{
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class Program
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{
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private static XPathDocumentdoc;
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private static XPathNavigatornav;
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static void Main( string []args)
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{
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doc= new XPathDocument(@ "..\..\books.xml" );
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nav=((IXPathNavigable)doc).CreateNavigator();
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SearchByGenre( "nove" );
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TotalPrice();
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Insert();
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Console.ReadLine();
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}
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public static void SearchByGenre( string search)
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{
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//查询bookstore的子元素book中genre属性值为novel的所有节点
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XPathNodeIteratoriter=nav.Select( "/bookstore/book[@genre='" +search+ "l']" );
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Console.WriteLine( "\nSearchByGenre:\n" );
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while (iter.MoveNext())
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{
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//迭代所有子代节点
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XPathNodeIteratornewIter=iter.Current.SelectDescendants(XPathNodeType.Element, false );
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while (newIter.MoveNext())
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{
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Console.WriteLine(newIter.Current.Name+ ":" +newIter.Current.Value);
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}
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}
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}
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public static void TotalPrice()
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{
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XPathNodeIteratoriter=nav.Select( "/bookstore/book" );
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Console.WriteLine( "\nTotalPrice:\n" );
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while (iter.MoveNext())
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{
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XPathNodeIteratornewIter=iter.Current.SelectDescendants(XPathNodeType.Element, false );
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while (newIter.MoveNext())
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{
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if (newIter.Current.Name== "price" )
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{
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Console.WriteLine(newIter.Current.Name+ ":" +newIter.Current.Value);
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}
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}
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}
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//统计图书总价
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Console.WriteLine( "Totalprice={0}" ,nav.Evaluate( "sum(bookstore/book/price)" ));
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}
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//插入节点
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public static void Insert()
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{
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XmlDocumentdoc= new XmlDocument();
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doc.Load(@ "..\..\books.xml" );
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XPathNavigatornav2=doc.CreateNavigator();
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//判断是否可编辑
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if (nav2.CanEdit)
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{
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XPathNodeIteratoriter=nav2.Select( "bookstore/book/price" );
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while (iter.MoveNext())
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{
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//在当前节点之后插入新节点
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iter.Current.InsertAfter( "<disc>5</disc>" );
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}
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}
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doc.Save(@ "..\..\newBooks.xml" );
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Console.WriteLine( "\nnewBooks.xmlsavedsuccessful.\n" );
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}
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}
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}
book.xml:
newBooks.xml:编辑后的文档
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<? xml version = "1.0" encoding = "utf-8" ?>
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< bookstore >
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< book genre = "autobiography" publicationdate = "1991" ISBN = "1-861003-11-0" >
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< title >TheAutobiographyofBenjaminFranklin</ title >
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< author >
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< first-name >Benjamin</ first-name >
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< last-name >Franklin</ last-name >
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</ author >
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< price >8.99</ price >
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</ book >
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< book genre = "novel" publicationdate = "1967" ISBN = "0-201-63361-2" >
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< title >TheConfidenceMan</ title >
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< author >
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< first-name >Herman</ first-name >
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< last-name >Melville</ last-name >
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</ author >
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< price >11.99</ price >
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</ book >
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< book genre = "philosophy" publicationdate = "1991" ISBN = "1-861001-57-6" >
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< title >TheGorgias</ title >
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< author >
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< name >Plato</ name >
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</ author >
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< price >9.99</ price >
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</ book >
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</ bookstore >
newBooks.xml:编辑后的文档
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<? xml version = "1.0" encoding = "utf-8" ?>
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< bookstore >
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< book genre = "autobiography" publicationdate = "1991" ISBN = "1-861003-11-0" >
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< title >TheAutobiographyofBenjaminFranklin</ title >
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< author >
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< first-name >Benjamin</ first-name >
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< last-name >Franklin</ last-name >
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</ author >
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< price >8.99</ price >
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< disc >5</ disc >
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</ book >
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< book genre = "novel" publicationdate = "1967" ISBN = "0-201-63361-2" >
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< title >TheConfidenceMan</ title >
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< author >
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< first-name >Herman</ first-name >
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< last-name >Melville</ last-name >
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</ author >
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< price >11.99</ price >
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< disc >5</ disc >
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</ book >
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< book genre = "philosophy" publicationdate = "1991" ISBN = "1-861001-57-6" >
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< title >TheGorgias</ title >
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< author >
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< name >Plato</ name >
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</ author >
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< price >9.99</ price >
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< disc >5</ disc >
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</ book >
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</ bookstore >