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>
1、往<bookstore>节点中插入一个<book>节点：
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")
//===============================================
结果为：
<?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>
<book genre="李赞红" ISBN="2-3631-4">
<title>CS从入门到精通</title>
<author>候捷</author>
<price>58.3</price>
</book>
</bookstore>
2、修改节点：将genre属性值为“李赞红“的节点的genre值改为“update李赞红”，将该节点的子节点<author>的文本修改为“亚胜”。
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
