XmlDocument 类

定义

public ref class XmlDocument : System::Xml::XmlNode

public class XmlDocument : System.Xml.XmlNode

type XmlDocument = class
    inherit XmlNode

Public Class XmlDocument
Inherits XmlNode

继承

Object

XmlNode

XmlDocument

派生

System.Configuration.ConfigXmlDocument

System.Xml.XmlDataDocument

注解

该 XmlDocument 类是 XML 文档的内存中表示形式。 它实现 W3C XML 文档对象模型 （DOM） 级别 1 核心和核心 DOM 级别 2。

DOM 表示 文档对象模型。 若要详细了解它，请参阅 XML 文档对象模型（DOM）。

可以使用类将 XML 加载到 DOM XmlDocument 中，然后以编程方式读取、修改和删除文档中的 XML。

如果你想要打开 XmlDocument 类并查看其实现方式，可以参考 参考资料。

将 XML 加载到文档对象模型中

让我们从以下这个 XML 文档入手，该文档的集合中包含几本书籍。 它包含可在任何 XML 文档中找到的基本内容，包括命名空间、表示数据的元素以及描述数据的属性。

<?xml version="1.0" encoding="utf-8"?>
<books xmlns="http://www.contoso.com/books">
  <book genre="novel" ISBN="1-861001-57-8" publicationdate="1823-01-28">
    <title>Pride And Prejudice</title>
    <price>24.95</price>
  </book>
  <book genre="novel" ISBN="1-861002-30-1" publicationdate="1985-01-01">
    <title>The Handmaid's Tale</title>
    <price>29.95</price>
  </book>
  <book genre="novel" ISBN="1-861001-45-3" publicationdate="1811-01-01">
    <title>Sense and Sensibility</title>
    <price>19.95</price>
  </book>
</books>

接下来，将此数据加载到 DOM 中，以便在内存中使用它。 执行此作的最常用方法是引用本地计算机或网络上的文件。

此示例从文件加载 XML。 如果文件不存在，它只会生成一些 XML 并加载该文件。

XmlDocument doc = new XmlDocument();
doc.PreserveWhitespace = true;
try { doc.Load("booksData.xml"); }
catch (System.IO.FileNotFoundException)
{
    doc.LoadXml("<?xml version=\"1.0\"?> \n" +
    "<books xmlns=\"http://www.contoso.com/books\"> \n" +
    "  <book genre=\"novel\" ISBN=\"1-861001-57-8\" publicationdate=\"1823-01-28\"> \n" +
    "    <title>Pride And Prejudice</title> \n" +
    "    <price>24.95</price> \n" +
    "  </book> \n" +
    "  <book genre=\"novel\" ISBN=\"1-861002-30-1\" publicationdate=\"1985-01-01\"> \n" +
    "    <title>The Handmaid's Tale</title> \n" +
    "    <price>29.95</price> \n" +
    "  </book> \n" +
    "</books>");
}

Dim doc As XmlDocument = New XmlDocument
doc.PreserveWhitespace = True
Try
    doc.Load("booksData.xml")
Catch ex As System.IO.FileNotFoundException
    ' If no file is found, generate some XML.
    doc.LoadXml("<?xml version=""1.0""?> " & ControlChars.NewLine & _
        "<books xmlns=""http://www.contoso.com/books""> " & ControlChars.NewLine & _
        "  <book genre=""novel"" ISBN=""1-861001-57-8"" publicationdate=""1823-01-28""> " & ControlChars.NewLine & _
        "    <title>Pride And Prejudice</title> " & ControlChars.NewLine & _
        "    <price>24.95</price> " & ControlChars.NewLine & _
        "  </book> " & ControlChars.NewLine & _
        "  <book genre=""novel"" ISBN=""1-861002-30-1"" publicationdate=""1985-01-01""> " & ControlChars.NewLine & _
        "    <title>The Handmaid's Tale</title> " & ControlChars.NewLine & _
        "    <price>29.95</price> " & ControlChars.NewLine & _
        "  </book> " & ControlChars.NewLine & _
        "</books>")
End Try

有关详细信息，请参阅 将 XML 文档读取到 DOM 中。

根据架构验证它

从如下所示的 XML 架构开始。 此架构定义 XML 中的数据类型以及哪些属性是必需的。

<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
  attributeFormDefault="unqualified"
  elementFormDefault="qualified"
  targetNamespace="http://www.contoso.com/books">
  <xs:element name="books">
    <xs:complexType>
      <xs:sequence>
        <xs:element maxOccurs="unbounded" name="book">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="title" type="xs:string" />
              <xs:element name="price" type="xs:decimal" />
            </xs:sequence>
            <xs:attribute name="genre" type="xs:string" use="required" />
            <xs:attribute name="ISBN" type="xs:string" use="required" />
            <xs:attribute name="publicationdate" type="xs:date" use="required" />
          </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

使用架构创建对象 XmlReader ，然后将该对象加载到 DOM 中。 创建一个事件处理程序，当代码尝试以违反架构规则的方式修改 XML 文件时执行。

这些代码块展示了执行所有这些工作所需的辅助方法。

//************************************************************************************
//
//  Helper method that generates an XML string.
//
//************************************************************************************
private string generateXMLString()
{
    string xml = "<?xml version=\"1.0\"?> \n" +
        "<books xmlns=\"http://www.contoso.com/books\"> \n" +
        "  <book genre=\"novel\" ISBN=\"1-861001-57-8\" publicationdate=\"1823-01-28\"> \n" +
        "    <title>Pride And Prejudice</title> \n" +
        "    <price>24.95</price> \n" +
        "  </book> \n" +
        "  <book genre=\"novel\" ISBN=\"1-861002-30-1\" publicationdate=\"1985-01-01\"> \n" +
        "    <title>The Handmaid's Tale</title> \n" +
        "    <price>29.95</price> \n" +
        "  </book> \n" +
        "  <book genre=\"novel\" ISBN=\"1-861001-45-3\" publicationdate=\"1811-01-01\"> \n" +
        "    <title>Sense and Sensibility</title> \n" +
        "    <price>19.95</price> \n" +
        "  </book> \n" +
        "</books>";
    return xml;
}

//************************************************************************************
//
//  Associate the schema with XML. Then, load the XML and validate it against
//  the schema.
//
//************************************************************************************
public XmlDocument LoadDocumentWithSchemaValidation(bool generateXML, bool generateSchema)
{
    XmlReader reader = null;
    XmlReaderSettings settings = new XmlReaderSettings();
    // Helper method to retrieve schema.
    XmlSchema schema = getSchema(generateSchema);

    settings.Schemas.Add(schema);
    settings.ValidationEventHandler += ValidationCallback;
    settings.ValidationFlags =
        settings.ValidationFlags | XmlSchemaValidationFlags.ReportValidationWarnings;
    settings.ValidationType = ValidationType.Schema;
    if (!generateXML)
    {
        try
        {
            reader = XmlReader.Create("booksData.xml", settings);
        }
        catch (FileNotFoundException ex)
        {
            Console.WriteLine(
                $"XML file not found so generating: {ex.Message}");
            generateXML = true;
        }
    }

    if (generateXML)
    {
        string xml = generateXMLString();
        StringReader stringReader = new StringReader(xml);

        reader = XmlReader.Create(stringReader, settings);
    }

    XmlDocument doc = new XmlDocument();

    doc.PreserveWhitespace = true;
    doc.Load(reader);
    reader.Close();

    return doc;
}

//************************************************************************************
//
//  Helper method that generates an XML Schema.
//
//************************************************************************************
private string generateXMLSchema()
{
    string xmlSchema =
        "<?xml version=\"1.0\" encoding=\"utf-8\"?> " +
        "<xs:schema attributeFormDefault=\"unqualified\" " +
        "elementFormDefault=\"qualified\" targetNamespace=\"http://www.contoso.com/books\" " +
        "xmlns:xs=\"http://www.w3.org/2001/XMLSchema\"> " +
        "<xs:element name=\"books\"> " +
        "<xs:complexType> " +
        "<xs:sequence> " +
        "<xs:element maxOccurs=\"unbounded\" name=\"book\"> " +
        "<xs:complexType> " +
        "<xs:sequence> " +
        "<xs:element name=\"title\" type=\"xs:string\" /> " +
        "<xs:element name=\"price\" type=\"xs:decimal\" /> " +
        "</xs:sequence> " +
        "<xs:attribute name=\"genre\" type=\"xs:string\" use=\"required\" /> " +
        "<xs:attribute name=\"publicationdate\" type=\"xs:date\" use=\"required\" /> " +
        "<xs:attribute name=\"ISBN\" type=\"xs:string\" use=\"required\" /> " +
        "</xs:complexType> " +
        "</xs:element> " +
        "</xs:sequence> " +
        "</xs:complexType> " +
        "</xs:element> " +
        "</xs:schema> ";
    return xmlSchema;
}

//************************************************************************************
//
//  Helper method that gets a schema
//
//************************************************************************************
private XmlSchema getSchema(bool generateSchema)
{
    XmlSchemaSet xs = new XmlSchemaSet();
    XmlSchema schema = null;

    if (!generateSchema)
    {
        try
        {
            schema = xs.Add("http://www.contoso.com/books", "booksData.xsd");
        }
        catch (FileNotFoundException ex)
        {
            Console.WriteLine(
                $"XSD file not found so generating: {ex.Message}");
            generateSchema = true;
        }
    }

    if (generateSchema)
    {
        string xmlSchemaString = generateXMLSchema();
        StringReader stringReader = new StringReader(xmlSchemaString);
        XmlReader reader = XmlReader.Create(stringReader);

        schema = xs.Add("http://www.contoso.com/books", reader);
    }

    return schema;
}

//************************************************************************************
//
//  Helper method to validate the XML against the schema.
//
//************************************************************************************
private void validateXML(bool generateSchema, XmlDocument doc)
{
    if (doc.Schemas.Count == 0)
    {
        // Helper method to retrieve schema.
        XmlSchema schema = getSchema(generateSchema);
        doc.Schemas.Add(schema);
    }

    // Use a callback to validate the XML node against the schema.
    doc.Validate(ValidationCallback);
}

//************************************************************************************
//
//  Event handler that is raised when XML doesn't validate against the schema.
//
//************************************************************************************
void ValidationCallback(object sender,
    System.Xml.Schema.ValidationEventArgs e)
{
    if (e.Severity == XmlSeverityType.Warning)
    {
        Console.WriteLine
            ("The following validation warning occurred: " + e.Message);
    }
    else if (e.Severity == XmlSeverityType.Error)
    {
        Console.WriteLine
            ("The following critical validation errors occurred: " + e.Message);
    }
}

'************************************************************************************
'
'  Associate the schema with XML. Then, load the XML and validate it against
'  the schema.
'
'************************************************************************************
Public Function LoadDocumentWithSchemaValidation(ByVal generateXML As Boolean, ByVal generateSchema As Boolean) As XmlDocument
    Dim reader As XmlReader
    Dim settings As XmlReaderSettings = New XmlReaderSettings
    ' Helper method to retrieve schema.
    Dim schema As XmlSchema = getSchema(generateSchema)
    If (schema Is Nothing) Then
        Return Nothing
    End If
    settings.Schemas.Add(schema)
    AddHandler settings.ValidationEventHandler, AddressOf settings_ValidationEventHandler
    settings.ValidationFlags = (settings.ValidationFlags Or XmlSchemaValidationFlags.ReportValidationWarnings)
    settings.ValidationType = ValidationType.Schema
    Try
        reader = XmlReader.Create("booksData.xml", settings)
    Catch ex As System.IO.FileNotFoundException
        If generateXML Then
            Dim xml As String = generateXMLString()
            Dim byteArray() As Byte = Encoding.UTF8.GetBytes(xml)
            Dim stream As MemoryStream = New MemoryStream(byteArray)
            reader = XmlReader.Create(stream, settings)
        Else
            Return Nothing
        End If
    End Try
    Dim doc As XmlDocument = New XmlDocument
    doc.PreserveWhitespace = True
    doc.Load(reader)
    reader.Close()
    Return doc
End Function

'************************************************************************************
'
'  Helper method that generates an XML Schema.
'
'************************************************************************************
Private Function generateXMLSchema() As String

    Dim generatedXmlSchema As String = "<?xml version=""1.0"" encoding=""utf-8""?> " & _
            "<xs:schema attributeFormDefault=""unqualified"" " & _
            "elementFormDefault=""qualified"" targetNamespace=""http://www.contoso.com/books"" " & _
            "xmlns:xs=""http://www.w3.org/2001/XMLSchema""> " & _
            "<xs:element name=""books""> " & _
            "<xs:complexType> " & _
            "<xs:sequence> " & _
            "<xs:element maxOccurs=""unbounded"" name=""book""> " & _
            "<xs:complexType> " & _
            "<xs:sequence> " & _
            "<xs:element name=""title"" type=""xs:string"" /> " & _
            "<xs:element name=""price"" type=""xs:decimal"" /> " & _
            "</xs:sequence> " & _
            "<xs:attribute name=""genre"" type=""xs:string"" use=""required"" /> " & _
            "<xs:attribute name=""publicationdate"" type=""xs:date"" use=""required"" /> " & _
            "<xs:attribute name=""ISBN"" type=""xs:string"" use=""required"" /> " & _
            "</xs:complexType> " & _
            "</xs:element> " & _
            "</xs:sequence> " & _
            "</xs:complexType> " & _
            "</xs:element> " & _
            "</xs:schema> "


    Return generatedXmlSchema

End Function

'************************************************************************************
'
'  Helper method that gets a schema
'
'************************************************************************************
Private Function getSchema(ByVal generateSchema As Boolean) As XmlSchema
    Dim xs As XmlSchemaSet = New XmlSchemaSet
    Dim schema As XmlSchema
    Try
        schema = xs.Add("http://www.contoso.com/books", "booksData.xsd")
    Catch ex As System.IO.FileNotFoundException
        If generateSchema Then
            Dim xmlSchemaString As String = generateXMLSchema()
            Dim byteArray() As Byte = Encoding.UTF8.GetBytes(xmlSchemaString)
            Dim stream As MemoryStream = New MemoryStream(byteArray)
            Dim reader As XmlReader = XmlReader.Create(stream)
            schema = xs.Add("http://www.contoso.com/books", reader)
        Else
            Return Nothing
        End If
    End Try
    Return schema
End Function

'************************************************************************************
'
'  Helper method to validate the XML against the schema.
'
'************************************************************************************
Private Sub validateXML(ByVal generateSchema As Boolean, ByVal doc As XmlDocument)
    If (doc.Schemas.Count = 0) Then
        ' Helper method to retrieve schema.
        Dim schema As XmlSchema = getSchema(generateSchema)
        doc.Schemas.Add(schema)
    End If
    ' Use an event handler to validate the XML node against the schema.
    doc.Validate(AddressOf settings_ValidationEventHandler)
End Sub

'************************************************************************************
'
'  Event handler that is raised when XML doesn't validate against the schema.
'
'************************************************************************************
Private Sub settings_ValidationEventHandler(ByVal sender As Object, ByVal e As System.Xml.Schema.ValidationEventArgs)
    If (e.Severity = XmlSeverityType.Warning) Then
        System.Windows.Forms.MessageBox.Show(("The following validation warning occurred: " & e.Message))
    ElseIf (e.Severity = XmlSeverityType.Error) Then
        System.Windows.Forms.MessageBox.Show(("The following critical validation errors occurred: " & e.Message))
        Dim objectType As Type = sender.GetType
    End If
End Sub

有关详细信息，请参阅 在 DOM 中验证 XML 文档。

浏览文档树

可以使用属性在 XML 文档周围导航。 但在使用其中任何一个之前，让我们快速回顾一些术语。 文档由节点组成。 每个节点都有一个直接位于其上方的 单个父 节点。 没有父节点的唯一节点是文档根，因为它是顶级节点。 大多数节点可以有 子 节点，即它们正下方的节点。 同一级别的节点是 同级节点。

以下示例演示如何获取根节点、跳转到根节点的第一个子节点、访问其任何子节点、返回到父节点，然后跨同级节点导航。

从根节点开始

此示例获取根节点，然后使用该节点将文档的内容输出到控制台。

using System;
using System.IO;
using System.Xml;

public class Sample
{
  public static void Main()
  {
    //Create the XmlDocument.
    XmlDocument doc = new XmlDocument();
    doc.LoadXml("<?xml version='1.0' ?>" +
                "<book genre='novel' ISBN='1-861001-57-5'>" +
                "<title>Pride And Prejudice</title>" +
                "</book>");

    //Display the document element.
    Console.WriteLine(doc.DocumentElement.OuterXml);
 }
}

Option Strict On
Option Explicit On
Imports System.Xml

Public Class ElementSample
    Public Shared Sub Main()
        'Create the XmlDocument.
        Dim doc As New XmlDocument()
        doc.LoadXml("<?xml version='1.0' ?>" &
                    "<book genre='novel' ISBN='1-861001-57-5'>" &
                    "<title>Pride And Prejudice</title>" &
                    "</book>")

        'Display the document element.
        Console.WriteLine(doc.DocumentElement.OuterXml)
    End Sub
End Class

获取子节点

此示例跳转到根节点的第一个子节点，然后循环访问该节点的子节点（如果有）。

using System;
using System.Xml;

public class Sample2
{
    public static void Main()
    {
        XmlDocument doc = new XmlDocument();
        doc.LoadXml("<book ISBN='1-861001-57-5'>" +
                    "<title>Pride And Prejudice</title>" +
                    "<price>19.95</price>" +
                    "</book>");

        XmlNode root = doc.FirstChild;

        //Display the contents of the child nodes.
        if (root.HasChildNodes)
        {
            for (int i = 0; i < root.ChildNodes.Count; i++)
            {
                Console.WriteLine(root.ChildNodes[i].InnerText);
            }
        }
    }
}

Option Strict
Option Explicit

Imports System.IO
Imports System.Xml

Public Class Sample

    Public Shared Sub Main()

        Dim doc As New XmlDocument()
        doc.LoadXml("<book ISBN='1-861001-57-5'>" & _
                    "<title>Pride And Prejudice</title>" & _
                    "<price>19.95</price>" & _
                    "</book>")

        Dim root As XmlNode = doc.FirstChild

        'Display the contents of the child nodes.
        If root.HasChildNodes Then
            Dim i As Integer
            For i = 0 To root.ChildNodes.Count - 1
                Console.WriteLine(root.ChildNodes(i).InnerText)
            Next i
        End If
    End Sub
End Class

返回到父节点

使用 ParentNode 属性。

请参阅最后一个子节点

本示例将书籍的价格写入控制台。 价格节点是书籍节点的最后一个子节点。

using System;
using System.Xml;

public class Sample3
{
    public static void Main()
    {
        XmlDocument doc = new XmlDocument();
        doc.LoadXml("<book ISBN='1-861001-57-5'>" +
                    "<title>Pride And Prejudice</title>" +
                    "<price>19.95</price>" +
                    "</book>");

        XmlNode root = doc.FirstChild;

        Console.WriteLine("Display the price element...");
        Console.WriteLine(root.LastChild.OuterXml);
    }
}

Option Explicit On
Option Strict On
Imports System.Xml

Public Class LastChildSample
    Public Shared Sub Main()

        Dim doc As New XmlDocument()
        doc.LoadXml("<book ISBN='1-861001-57-5'>" &
                    "<title>Pride And Prejudice</title>" &
                    "<price>19.95</price>" &
                    "</book>")

        Dim root As XmlNode = doc.FirstChild

        Console.WriteLine("Display the price element...")
        Console.WriteLine(root.LastChild.OuterXml)
    End Sub
End Class

在同级节点之间向前导航

本例将从书籍前进到书籍。 书籍节点彼此为同级节点。

using System;
using System.Xml;

public class Sample4
{
    public static void Main()
    {
        XmlDocument doc = new XmlDocument();
        doc.Load("books.xml");

        XmlNode currNode = doc.DocumentElement.FirstChild;
        Console.WriteLine("First book...");
        Console.WriteLine(currNode.OuterXml);

        XmlNode nextNode = currNode.NextSibling;
        Console.WriteLine("\r\nSecond book...");
        Console.WriteLine(nextNode.OuterXml);
    }
}

Imports System.Xml

Public Class NextSiblingSample
    Public Shared Sub Main()

        Dim doc As XmlDocument = New XmlDocument()
        doc.Load("books.xml")

        Dim currNode As XmlNode = doc.DocumentElement.FirstChild
        Console.WriteLine("First book...")
        Console.WriteLine(currNode.OuterXml)

        Dim nextNode As XmlNode = currNode.NextSibling
        Console.WriteLine(ControlChars.Lf + "Second book...")
        Console.WriteLine(nextNode.OuterXml)

    End Sub
End Class

在同级节点之间向后导航

本例将从书籍后退到书籍。

using System;
using System.Xml;

public class Sample {

  public static void Main() {

      XmlDocument doc = new XmlDocument();
      doc.Load("books.xml");

      XmlNode lastNode = doc.DocumentElement.LastChild;
      Console.WriteLine("Last book...");
      Console.WriteLine(lastNode.OuterXml);

      XmlNode prevNode = lastNode.PreviousSibling;
      Console.WriteLine("\r\nPrevious book...");
      Console.WriteLine(prevNode.OuterXml);
  }
}

Imports System.Xml

Public Class Sample5
    Public Shared Sub Main()
        Dim doc As XmlDocument = New XmlDocument()
        doc.Load("books.xml")

        Dim lastNode As XmlNode = doc.DocumentElement.LastChild
        Console.WriteLine("Last book...")
        Console.WriteLine(lastNode.OuterXml)

        Dim prevNode As XmlNode = lastNode.PreviousSibling
        Console.WriteLine(ControlChars.Lf + "Previous book...")
        Console.WriteLine(prevNode.OuterXml)
    End Sub
End Class

查找节点

查找一个或多个数据节点的最常用方法是使用 XPath 查询字符串，但也有不需要的方法。

获取单个节点

此示例使用 ISBN 编号查找书籍。

public XmlNode GetBook(string uniqueAttribute, XmlDocument doc)
{
    XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
    nsmgr.AddNamespace("bk", "http://www.contoso.com/books");
    string xPathString = "//bk:books/bk:book[@ISBN='" + uniqueAttribute + "']";
    XmlNode xmlNode = doc.DocumentElement.SelectSingleNode(xPathString, nsmgr);
   return xmlNode;
}

Public Function GetBook(ByVal uniqueAttribute As String, ByVal doc As XmlDocument) As XmlNode
    Dim nsmgr As XmlNamespaceManager = New XmlNamespaceManager(doc.NameTable)
    nsmgr.AddNamespace("bk", "http://www.contoso.com/books")
    Dim xPathString As String = ("//bk:books/bk:book[@ISBN='" _
                & (uniqueAttribute & "']"))
    Dim xmlNode As XmlNode = doc.DocumentElement.SelectSingleNode(xPathString, nsmgr)
    Return xmlNode
End Function

此示例中使用的字符串是 Xpath 查询。 可以在 XPath 示例中找到更多示例。

可以使用GetElementById来检索节点。 若要使用此方法，必须在 XML 文件的文档类型定义声明中定义 ID。

获取节点后，将获取属性或子节点的值。 本例使用书籍节点执行此操作。

public void GetBookInformation(ref string title, ref string ISBN, ref string publicationDate,
    ref string price, ref string genre, XmlNode book)
{
    XmlElement bookElement = (XmlElement)book;

    // Get the attributes of a book.
    XmlAttribute attr = bookElement.GetAttributeNode("ISBN");
    ISBN = attr.InnerXml;

    attr = bookElement.GetAttributeNode("genre");
    genre = attr.InnerXml;

    attr = bookElement.GetAttributeNode("publicationdate");
    publicationDate = attr.InnerXml;

    // Get the values of child elements of a book.
    title = bookElement["title"].InnerText;
    price = bookElement["price"].InnerText;
}

Public Sub GetBookInformation(ByRef title As String, ByRef ISBN As String, ByRef publicationDate As String, ByRef price As String, ByRef genre As String, ByVal book As XmlNode)
    Dim bookElement As XmlElement = CType(book, XmlElement)
    ' Get the attributes of a book.
    Dim attr As XmlAttribute = bookElement.GetAttributeNode("ISBN")
    ISBN = attr.InnerXml
    attr = bookElement.GetAttributeNode("genre")
    genre = attr.InnerXml
    attr = bookElement.GetAttributeNode("publicationdate")
    publicationDate = attr.InnerXml
    ' Get the values of child elements of a book.
    title = bookElement("title").InnerText
    price = bookElement("price").InnerText
End Sub

获取节点集合

本示例选择作者姓氏为 Austen 的所有书籍，然后更改这些书籍的价格。

using System;
using System.Xml;

public class Sample6
{
    public static void Main()
    {
        XmlDocument doc = new XmlDocument();
        doc.Load("booksort.xml");

        XmlNodeList nodeList;
        XmlNode root = doc.DocumentElement;

        nodeList = root.SelectNodes("descendant::book[author/last-name='Austen']");

        //Change the price on the books.
        foreach (XmlNode book in nodeList)
        {
            book.LastChild.InnerText = "15.95";
        }

        Console.WriteLine("Display the modified XML document....");
        doc.Save(Console.Out);
    }
}

Imports System.IO
Imports System.Xml

public class Sample

  public shared sub Main()

    'Create the XmlDocument.
    Dim doc as XmlDocument = new XmlDocument()
    doc.Load("booksort.xml")

    Dim book as XmlNode
    Dim nodeList as XmlNodeList
    Dim root as XmlNode = doc.DocumentElement

    nodeList=root.SelectNodes("descendant::book[author/last-name='Austen']")

    'Change the price on the books.
    for each book in nodeList
      book.LastChild.InnerText="15.95"
    next

    Console.WriteLine("Display the modified XML document....")
    doc.Save(Console.Out)

  end sub
end class

还可以使用节点的名称获取节点的集合。 例如，此示例获取所有书籍标题的集合。

using System;
using System.Xml;

public class Sample1
{
    public static void Main()
    {
        //Create the XmlDocument.
        XmlDocument doc = new XmlDocument();
        doc.Load("books.xml");

        //Display all the book titles.
        XmlNodeList elemList = doc.GetElementsByTagName("title");
        for (int i = 0; i < elemList.Count; i++)
        {
            Console.WriteLine(elemList[i].InnerXml);
        }
    }
}

Option Explicit On
Option Strict On
Imports System.Xml

Public Class TagSample

    Public Shared Sub Main()
        'Create the XmlDocument.
        Dim doc As New XmlDocument()
        doc.Load("books.xml")

        'Display all the book titles.
        Dim elemList As XmlNodeList = doc.GetElementsByTagName("title")
        Dim i As Integer
        For i = 0 To elemList.Count - 1
            Console.WriteLine(elemList(i).InnerXml)
        Next i
    End Sub
End Class

有关详细信息，请参阅 使用 XPath 导航选择节点。

编辑节点

本例将编辑书籍节点及其属性。

public void editBook(string title, string ISBN, string publicationDate,
    string genre, string price, XmlNode book, bool validateNode, bool generateSchema)
{

    XmlElement bookElement = (XmlElement)book;

    // Get the attributes of a book.
    bookElement.SetAttribute("ISBN", ISBN);
    bookElement.SetAttribute("genre", genre);
    bookElement.SetAttribute("publicationdate", publicationDate);

    // Get the values of child elements of a book.
    bookElement["title"].InnerText = title;
    bookElement["price"].InnerText = price;

    if (validateNode)
    {
        validateXML(generateSchema, bookElement.OwnerDocument);
    }
}

Public Sub editBook(ByVal title As String, ByVal ISBN As String,
                    ByVal publicationDate As String, ByVal genre As String,
                    ByVal price As String, ByVal book As XmlNode, ByVal validateNode As Boolean,
                    ByVal generateSchema As Boolean)

    Dim bookElement As XmlElement = CType(book, XmlElement)

    ' Get the attributes of a book.
    bookElement.SetAttribute("ISBN", ISBN)
    bookElement.SetAttribute("genre", genre)
    bookElement.SetAttribute("publicationdate", publicationDate)

    ' Get the values of child elements of a book.
    bookElement("title").InnerText = title
    bookElement("price").InnerText = price
    If validateNode Then
        validateXML(generateSchema, bookElement.OwnerDocument)
    End If

End Sub

有关详细信息，请参阅 修改 XML 文档中的节点、内容和值。

添加节点

若要添加节点，请使用 CreateElement 该方法或 CreateNode 方法。

若要添加数据节点（如书籍），请使用 CreateElement 该方法。

对于任何其他类型的节点（例如注释、空格节点或 CDATA 节点），请使用该方法 CreateNode 。

此示例创建书籍节点，向该节点添加属性，然后将该节点添加到文档中。

public XmlElement AddNewBook(string genre, string ISBN, string misc,
    string title, string price, XmlDocument doc)
{
    // Create a new book element.
    XmlElement bookElement = doc.CreateElement("book", "http://www.contoso.com/books");

    // Create attributes for book and append them to the book element.
    XmlAttribute attribute = doc.CreateAttribute("genre");
    attribute.Value = genre;
    bookElement.Attributes.Append(attribute);

    attribute = doc.CreateAttribute("ISBN");
    attribute.Value = ISBN;
    bookElement.Attributes.Append(attribute);

    attribute = doc.CreateAttribute("publicationdate");
    attribute.Value = misc;
    bookElement.Attributes.Append(attribute);

    // Create and append a child element for the title of the book.
    XmlElement titleElement = doc.CreateElement("title");
    titleElement.InnerText = title;
    bookElement.AppendChild(titleElement);

    // Introduce a newline character so that XML is nicely formatted.
    bookElement.InnerXml =
        bookElement.InnerXml.Replace(titleElement.OuterXml,
        "\n    " + titleElement.OuterXml + " \n    ");

    // Create and append a child element for the price of the book.
    XmlElement priceElement = doc.CreateElement("price");
    priceElement.InnerText= price;
    bookElement.AppendChild(priceElement);

    // Introduce a newline character so that XML is nicely formatted.
    bookElement.InnerXml =
        bookElement.InnerXml.Replace(priceElement.OuterXml, priceElement.OuterXml + "   \n  ");

    return bookElement;
}

Public Function AddNewBook(ByVal genre As String, ByVal ISBN As String, ByVal misc As String, ByVal title As String, ByVal price As String, ByVal doc As XmlDocument) As XmlElement
    ' Create a new book element.
    Dim bookElement As XmlElement = doc.CreateElement("book", "http://www.contoso.com/books")

    ' Create attributes for book and append them to the book element.
    Dim attribute As XmlAttribute = doc.CreateAttribute("genre")
    attribute.Value = genre
    bookElement.Attributes.Append(attribute)

    attribute = doc.CreateAttribute("ISBN")
    attribute.Value = ISBN
    bookElement.Attributes.Append(attribute)

    attribute = doc.CreateAttribute("publicationdate")
    attribute.Value = misc
    bookElement.Attributes.Append(attribute)

    ' Create and append a child element for the title of the book.
    Dim titleElement As XmlElement = doc.CreateElement("title")
    titleElement.InnerText = title
    bookElement.AppendChild(titleElement)

    ' Introduce a newline character so that XML is nicely formatted.
    bookElement.InnerXml = bookElement.InnerXml.Replace(titleElement.OuterXml, _
                           "\n   " & titleElement.OuterXml & " " & ControlChars.NewLine + "    ")
    ' Create and append a child element for the price of the book.
    Dim priceElement As XmlElement = doc.CreateElement("price")
    priceElement.InnerText = price
    bookElement.AppendChild(priceElement)

    ' Introduce a newline character so that XML is nicely formatted.
    bookElement.InnerXml = bookElement.InnerXml.Replace(priceElement.OuterXml,
                                                        (priceElement.OuterXml & "   " & ControlChars.NewLine & "  "))
    Return bookElement
End Function

有关详细信息，请参阅 将节点插入 XML 文档。

删除节点

若要删除节点，请使用 RemoveChild 该方法。

本示例从文档中删除书籍，以及书籍节点前显示的任何空格。

public void deleteBook(XmlNode book)
{
    XmlNode prevNode = book.PreviousSibling;

    book.OwnerDocument.DocumentElement.RemoveChild(book);

    if (prevNode.NodeType == XmlNodeType.Whitespace ||
        prevNode.NodeType == XmlNodeType.SignificantWhitespace)
    {
        prevNode.OwnerDocument.DocumentElement.RemoveChild(prevNode);
    }
}

Public Sub deleteBook(ByVal book As XmlNode)

    Dim prevNode As XmlNode = book.PreviousSibling
    book.OwnerDocument.DocumentElement.RemoveChild(book)

    If ((prevNode.NodeType = XmlNodeType.Whitespace) _
                OrElse (prevNode.NodeType = XmlNodeType.SignificantWhitespace)) Then
        prevNode.OwnerDocument.DocumentElement.RemoveChild(prevNode)

    End If
End Sub

有关详细信息，请参阅 从 XML 文档中删除节点、内容和值。

放置节点

可以使用InsertBefore和InsertAfter方法来选择节点在文档中显示的位置。

此示例显示了两个帮助程序方法。 其中一个将节点在列表中向上移动。 另一种用于在列表中向下移动节点。

这些方法可以在应用程序中使用，使用户可以在书籍列表中上下移动书籍。 当用户选择书籍并按向上或向下按钮时，代码可以调用此类方法来定位其他书籍节点之前或之后对应的书籍节点。

//************************************************************************************
//
//  Summary: Move elements up in the XML.
//
//
//************************************************************************************

public void MoveElementUp(XmlNode book)
{
    XmlNode previousNode = book.PreviousSibling;
    while (previousNode != null && (previousNode.NodeType != XmlNodeType.Element))
    {
        previousNode = previousNode.PreviousSibling;
    }
    if (previousNode != null)
    {
        XmlNode newLineNode = book.NextSibling;
        book.OwnerDocument.DocumentElement.RemoveChild(book);
        if (newLineNode.NodeType == XmlNodeType.Whitespace |
            newLineNode.NodeType == XmlNodeType.SignificantWhitespace)
        {
            newLineNode.OwnerDocument.DocumentElement.RemoveChild(newLineNode);
        }
        InsertBookElement((XmlElement)book, Constants.positionAbove,
            previousNode, false, false);
    }
}

//************************************************************************************
//
//  Summary: Move elements down in the XML.
//
//
//************************************************************************************
public void MoveElementDown(XmlNode book)
{
    // Walk backwards until we find an element - ignore text nodes
    XmlNode NextNode = book.NextSibling;
    while (NextNode != null && (NextNode.NodeType != XmlNodeType.Element))
    {
        NextNode = NextNode.NextSibling;
    }
    if (NextNode != null)
    {
        XmlNode newLineNode = book.PreviousSibling;
        book.OwnerDocument.DocumentElement.RemoveChild(book);
        if (newLineNode.NodeType == XmlNodeType.Whitespace |
            newLineNode.NodeType == XmlNodeType.SignificantWhitespace)
        {
            newLineNode.OwnerDocument.DocumentElement.RemoveChild(newLineNode);
        }

        InsertBookElement((XmlElement)book, Constants.positionBelow,
            NextNode, false, false);
    }
}

'************************************************************************************
'
'  Summary: Move elements up in the XML.
'
'
'************************************************************************************
Public Sub MoveElementUp(ByVal book As XmlNode)
    Dim previousNode As XmlNode = book.PreviousSibling

    While ((Not (previousNode) Is Nothing) _
                AndAlso (previousNode.NodeType <> XmlNodeType.Element))
        previousNode = previousNode.PreviousSibling

    End While
    If (Not (previousNode) Is Nothing) Then
        Dim newLineNode As XmlNode = book.NextSibling
        book.OwnerDocument.DocumentElement.RemoveChild(book)

        If ((newLineNode.NodeType = XmlNodeType.Whitespace) _
                    Or (newLineNode.NodeType = XmlNodeType.SignificantWhitespace)) Then
            newLineNode.OwnerDocument.DocumentElement.RemoveChild(newLineNode)
        End If

        InsertBookElement(CType(book, XmlElement), Constants.positionAbove,
                          previousNode, False, False)
    End If
End Sub

'************************************************************************************
'
'  Summary: Move elements down in the XML.
'
'
'************************************************************************************
Public Sub MoveElementDown(ByVal book As XmlNode)
    ' Walk backwards until we find an element - ignore text nodes
    Dim NextNode As XmlNode = book.NextSibling

    While ((Not (NextNode) Is Nothing) _
                AndAlso (NextNode.NodeType <> XmlNodeType.Element))
        NextNode = NextNode.NextSibling

    End While

    If (Not (NextNode) Is Nothing) Then
        Dim newLineNode As XmlNode = book.PreviousSibling
        book.OwnerDocument.DocumentElement.RemoveChild(book)

        If ((newLineNode.NodeType = XmlNodeType.Whitespace) _
                    Or (newLineNode.NodeType = XmlNodeType.SignificantWhitespace)) Then
            newLineNode.OwnerDocument.DocumentElement.RemoveChild(newLineNode)
        End If

        InsertBookElement(CType(book, XmlElement), Constants.positionBelow,
                          NextNode, False, False)
    End If
End Sub

另请参阅

• XmlNodeChangedEventHandler