<?xml version="1.0" encoding="gb2312"?>
<bookstore>
  <book ISBN="2-3631-4">
    <title>Oberon's   Legacy</title>
    <author>Corets,Eva</author>
    <price>5.95</price>
  </book>
</bookstore>

code：

Imports System.Xml

Public Class Form1

    Dim xmlDoc As New XmlDocument()

    Private Sub Button1_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button1.Click
        '往<bookstore>节点中插入一个<book>节点：

        xmlDoc.Load("bookstore.xml")
        Dim root As XmlNode = xmlDoc.SelectSingleNode("bookstore") '查找<bookstore>  
        Dim xe1 As XmlElement = xmlDoc.CreateElement("book") '创建一个<book>节点  
        xe1.SetAttribute("genre","李赞红") '设置该节点genre属性  
        xe1.SetAttribute("ISBN","2-3631-4") '设置该节点ISBN属性  
        Dim xesub1 As XmlElement = xmlDoc.CreateElement("title")
        xesub1.InnerText = "CS从入门到精通" '设置文本节点  
        xe1.AppendChild(xesub1) '添加到<book>节点中  
        Dim xesub2 As XmlElement = xmlDoc.CreateElement("author")
        xesub2.InnerText = "候捷"
        xe1.AppendChild(xesub2)
        Dim xesub3 As XmlElement = xmlDoc.CreateElement("price")
        xesub3.InnerText = "58.3"
        xe1.AppendChild(xesub3)

        root.AppendChild(xe1) '添加到<bookstore>节点中  
        xmlDoc.Save("bookstore.xml")
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button2.Click
        Dim nodeList As XmlNodeList = xmlDoc.SelectSingleNode("bookstore").ChildNodes '获取bookstore节点的所有子节点  
        Dim xn As XmlNode
        For Each xn In nodeList '遍历所有子节点  
            Dim xe As XmlElement = CType(xn,XmlElement) '将子节点类型转换为XmlElement类型  
            If xe.GetAttribute("genre") = "李赞红" Then '如果genre属性值为“李赞红”  
                xe.SetAttribute("genre","update李赞红") '则修改该属性为“update李赞红”  
                Dim nls As XmlNodeList = xe.ChildNodes '继续获取xe子节点的所有子节点  
                Dim xn1 As XmlNode
                For Each xn1 In nls '遍历  
                    Dim xe2 As XmlElement = CType(xn1,XmlElement) '转换类型  
                    If xe2.Name = "author" Then '如果找到  
                        xe2.InnerText = "亚胜" '则修改  
                        Exit For '找到退出来就可以了  
                    End If
                Next xn1
                Exit For
            End If
        Next xn

        xmlDoc.Save("bookstore.xml") '保存。
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button3.Click
        Dim xnl As XmlNodeList = xmlDoc.SelectSingleNode("bookstore").ChildNodes

        Dim xn As XmlNode
        For Each xn In xnl
            Dim xe As XmlElement = CType(xn,XmlElement)
            If xe.GetAttribute("genre") = "fantasy" Then
                xe.RemoveAttribute("genre") '删除genre属性  
            Else
                If xe.GetAttribute("genre") = "update李赞红" Then
                    xe.RemoveAll() '删除该节点的全部内容  
                End If
            End If
        Next xn
        xmlDoc.Save("bookstore.xml")
    End Sub

    Private Sub Button4_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button4.Click
        Dim xn As XmlNode = xmlDoc.SelectSingleNode("bookstore")

        Dim xnl As XmlNodeList = xn.ChildNodes

        Dim xnf As XmlNode
        For Each xnf In xnl
            Dim xe As XmlElement = CType(xnf,XmlElement)
            Console.WriteLine(xe.GetAttribute("genre")) '显示属性值  
            Console.WriteLine(xe.GetAttribute("ISBN"))

            Dim xnf1 As XmlNodeList = xe.ChildNodes
            Dim xn2 As XmlNode
            For Each xn2 In xnf1
                Console.WriteLine(xn2.InnerText) '显示子节点点文本  
            Next xn2
        Next xnf
    End Sub
End Class