[转自]http://tech.sina.com.cn/s/2008-07-07/1608722485.shtml

已知有一个XML文件（bookstore.xml）如下：

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

Dim xmlDoc As New XmlDocument()
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")

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 ForEach '找到退出来就可以了 
End If
Next xn1
Exit ForEach
End If
Next xn

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