原创地址:http://www.cnblogs.com/jfzhu/archive/2012/11/19/2778098.html
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W3C制定了XML DOM标准。很多编程语言中多提供了支持W3C XML DOM标准的API。我在之前的文章中介绍过如何使用Javascript对XML文档进行加载与查询。在本文中,我来介绍一下.Net中的XmlDocument类。它支持并扩展了W3C XML DOM标准。它将整个XML文档都先装载进内存中,然后再对XML文档进行操作,所以如果XML文档内容过大,不建议使用XmlDocument类,因为会消耗过多内存。对于很大的XML文档,可以使用XmlReader类来读取。因为XmlReader使用Steam(流)来读取文件,所以不会对内存造成太大的消耗。下面就来看一下如何使用XmlDocument类。
(一) 加载
加载XML比较常用的有三种方法:
public virtual void Load(string filename); public virtual void Load(Stream inStream); public virtual void LoadXml(string xml);
下面代码演示如何使用它们:
XmlDocument xmlDoc = new XmlDocument(); xmlDoc.Load("XMLFile1.xml"); Entity retrievedAnnotation = _orgService.Retrieve("annotation" , new Guid("C1B13C7F-F430-E211-8FA1-984BE1731399"), new ColumnSet(true)); byte[] fileContent = Convert.FromBase64String(retrievedAnnotation["documentbody"].ToString()); MemoryStream ms = new MemoryStream(fileContent); XmlDocument xmlDoc2 = new XmlDocument(); xmlDoc2.Load(ms); string str = @"<Customers><Customer id='01' city='Beijing' country='China' name='Lenovo'/></Customers>"; XmlDocument xmlDoc3 = new XmlDocument(); xmlDoc3.LoadXml(str);
(二) 查询
对XML的元素、属性、文本的查询可以使用XPath。具体的定义可以参看w3school。
首先应该了解一下XPath表达式:
表达式 | 描述 |
nodename | 选取此节点的所有子节点。 |
/ | 从根节点选取。 |
// | 从匹配选择的当前节点选择文档中的节点,而不考虑它们的位置。 |
. | 选取当前节点。 |
.. | 选取当前节点的父节点。 |
@ | 选取属性。 |
我们主要使用两个方法来查询XML文档,SelectNodes(xpath expression)和SelectSingleNode(xpath expression)。
SelectNodes返回一个XmlNodeList对象,也就是所有符合xpath表达式的xml节点都将会被返回,你需要对返回的结果进行遍历。
SelectSingleNode只返回第一个符合xpath表达式的节点,或者返回null。
以下面的XML文件为例,我们进行一些演示:
<?xml version="1.0" encoding="utf-8" ?> <Customers> <Customer id="01" city="Beijing" country="China" name="Lenovo"> <Contact gender="female" title="Support">Li Li</Contact> </Customer> <Customer id="02" city="Amsterdam" country="The Netherlands" name="Shell"> <Contact gender="male" title="Sales Person">Aaron Babbitt</Contact> <Contact gender="female" title="Sales Manager">Daisy Cabell</Contact> <Contact gender="male" title="Sales Person">Gabriel Eads</Contact> </Customer> </Customers>
1. 返回所有Contact节点:
XmlNodeList nodelist = xmlDoc.SelectNodes("/Customers/Customer/Contact"); foreach (XmlNode node in nodelist) { Console.WriteLine(node.OuterXml); }
输出结果为:
<Contact gender="female" title="Support">Li Li</Contact>
<Contact gender="male" title="Sales Person">Aaron Babbitt</Contact>
<Contact gender="female" title="Sales Manager">Daisy Cabell</Contact>
<Contact gender="male" title="Sales Person">Gabriel Eads</Contact>
2. 返回id为02的customer:
XmlNode node = xmlDoc.SelectSingleNode("/Customers/Customer[@id='02']"); Console.WriteLine(node.OuterXml);
输出结果为:
<Customer id="02" city="Amsterdam" country="The Netherlands" name="Shell">
<Contact gender="male" title="Sales Person">Aaron Babbitt</Contact>
<Contact gender="female" title="Sales Manager">Daisy Cabell</Contact>
<Contact gender="male" title="Sales Person">Gabriel Eads</Contact>
</Customer>
3. 返回含有contact名为Li Li的contact:
XmlNode node = xmlDoc.SelectSingleNode("/Customers/Customer/Contact[text()='Li Li']"); Console.WriteLine(node.OuterXml);
输出结果:
<Contact gender="female" title="Support">Li Li</Contact>
4. 返回含有contact名为 Li Li 的customer。注意和3的区别:
XmlNode node = xmlDoc.SelectSingleNode("/Customers/Customer[Contact/text()='Li Li']"); Console.WriteLine(node.OuterXml);
输出结果:
<Customer id="01" city="Beijing" country="China" name="Lenovo">
<Contact gender="female" title="Support">Li Li</Contact>
</Customer>
5. (1) 获取outer xml:
XmlNode node = xmlDoc.SelectSingleNode("/Customers/Customer[@id='02']");
Console.WriteLine(node.OuterXml);
(2) 获取 inner xml:
XmlNode node = xmlDoc.SelectSingleNode("/Customers/Customer[@id='02']");
Console.WriteLine(node.InnerXml);
(3) 获取 text
XmlNode node = xmlDoc.SelectSingleNode("/Customers/Customer/Contact[text()='Li Li']");
Console.WriteLine(node.InnerText);
(4) 获取属性
XmlNode node = xmlDoc.SelectSingleNode("/Customers/Customer/Contact[text()='Li Li']");
Console.WriteLine(node.Attributes["gender"].Value);
(三) 创建
以创建以下XML文档为例:
<?xml version="1.0" encoding="UTF-8"?> <Customers> <Customer id="01" name="Lenovo" country="China" city="Beijing"> <Contact title="Support" gender="female">Li Li</Contact> </Customer> </Customers>
var xmlDoc = new XmlDocument(); //Create the xml declaration first xmlDoc.AppendChild(xmlDoc.CreateXmlDeclaration("1.0", "utf-8", null)); //Create the root node and append into doc var el = xmlDoc.CreateElement("Customers"); xmlDoc.AppendChild(el); // Customer Lenovo XmlElement elementCustomer = xmlDoc.CreateElement("Customer"); XmlAttribute attrID = xmlDoc.CreateAttribute("id"); attrID.Value = "01"; elementCustomer.Attributes.Append(attrID); XmlAttribute cityID = xmlDoc.CreateAttribute("city"); cityID.Value = "Beijing"; elementCustomer.Attributes.Append(cityID); XmlAttribute attrCountry = xmlDoc.CreateAttribute("country"); attrCountry.Value = "China"; elementCustomer.Attributes.Append(attrCountry); XmlAttribute nameCountry = xmlDoc.CreateAttribute("name"); nameCountry.Value = "Lenovo"; elementCustomer.Attributes.Append(nameCountry); el.AppendChild(elementCustomer); // Contact Li Li XmlElement elementContact = xmlDoc.CreateElement("Contact"); elementContact.InnerText = "Li Li"; XmlAttribute attrGender = xmlDoc.CreateAttribute("gender"); attrGender.Value = "female"; elementContact.Attributes.Append(attrGender); XmlAttribute titleGender = xmlDoc.CreateAttribute("title"); titleGender.Value = "Support"; elementContact.Attributes.Append(titleGender); elementCustomer.AppendChild(elementContact); xmlDoc.Save("test.xml");
(四) 更改
还以下面的XML文档为例
<?xml version="1.0" encoding="utf-8" ?> <Customers> <Customer id="01" city="Beijing" country="China" name="Lenovo"> <Contact gender="female" title="Support">Li Li</Contact> </Customer> <Customer id="02" city="Amsterdam" country="The Netherlands" name="Shell"> <Contact gender="male" title="Sales Person">Aaron Babbitt</Contact> <Contact gender="female" title="Sales Manager">Daisy Cabell</Contact> <Contact gender="male" title="Sales Person">Gabriel Eads</Contact> </Customer> </Customers>
1. 将Contact Li Li更改为Evi
XmlNode node = xmlDoc.SelectSingleNode("/Customers/Customer/Contact[text()='Li Li']"); node.InnerText = "Evi";
2. 将id为02的Customer的city属性更改为Den Haag
XmlNode node = xmlDoc.SelectSingleNode("/Customers/Customer[@id='02']"); node.Attributes["city"].Value = "Den Haag";
3. 将id为02的Customer的所有下属Contact的title属性更改为Functional Consultant
XmlNode node = xmlDoc.SelectSingleNode("/Customers/Customer[@id='02']"); XmlNodeList nodelist = node.SelectNodes("./Contact"); foreach (XmlNode n in nodelist) { n.Attributes["title"].Value = "Functional Consultant"; }
(五) 删除节点
还是以这个XML文档为例
<?xml version="1.0" encoding="utf-8" ?> <Customers> <Customer id="01" city="Beijing" country="China" name="Lenovo"> <Contact gender="female" title="Support">Li Li</Contact> </Customer> <Customer id="02" city="Amsterdam" country="The Netherlands" name="Shell"> <Contact gender="male" title="Sales Person">Aaron Babbitt</Contact> <Contact gender="female" title="Sales Manager">Daisy Cabell</Contact> <Contact gender="male" title="Sales Person">Gabriel Eads</Contact> </Customer> </Customers>
1. 删除Contact Li Li节点
XmlNode node = xmlDoc.SelectSingleNode("/Customers/Customer/Contact[text()='Li Li']"); node.ParentNode.RemoveChild(node);
结果:
<?xml version="1.0" encoding="utf-8"?> <Customers> <Customer id="01" city="Beijing" country="China" name="Lenovo"> </Customer> <Customer id="02" city="Amsterdam" country="The Netherlands" name="Shell"> <Contact gender="male" title="Sales Person">Aaron Babbitt</Contact> <Contact gender="female" title="Sales Manager">Daisy Cabell</Contact> <Contact gender="male" title="Sales Person">Gabriel Eads</Contact> </Customer> </Customers>
(六) Namespace
XML文档中如果使用了命名空间该如何进行查询,以下面的文档为例:
<?xml version="1.0" encoding="utf-8" ?> <root xmlns:h="http://www.w3.org/TR/html4/" xmlns:f="http://www.w3schools.com/furniture"> <h:table> <h:tr> <h:td>Apples</h:td> <h:td>Bananas</h:td> </h:tr> </h:table> <f:table> <f:name>African Coffee Table</f:name> <f:width>80</f:width> <f:length>120</f:length> </f:table> </root>
查找第一个f:name节点
var names = new XmlNamespaceManager(xmlDoc.NameTable); names.AddNamespace("h", "http://www.w3.org/TR/html4/"); names.AddNamespace("f", "http://www.w3schools.com/furniture"); XmlNode node = xmlDoc.SelectSingleNode("/root/f:table/f:name", names); Console.WriteLine(node.InnerText);
总结: XmlDocument类是.Net API中提供的支持W3C XML DOM标准的类。可以用它来创建和查询XML文档。由于XmlDocument要将XML文档的内容全部装载进内存中,所以对于读取内容过大的XML文档,不适合使用XmlDocument类,而可以使用XmlReader来完成读取。