3使用XlmWrite把一个xml文件写入输出流中。在（demo2.aspx运行时显示xml文档）

protected void Page_Load(object sender, EventArgs e)
{
XmlWriterSettings settings=new XmlWriterSettings();
settings.Encoding=System.Text.Encoding.UTF8;
settings.Indent=true;
using (XmlWriter writer = XmlWriter.Create(Response.Output, settings))
{
writer.WriteStartDocument();//写头文件
writer.WriteStartElement("books");//写根节点
writer.WriteStartElement("book");//写子节点
writer.WriteStartAttribute("id");//给子节点增加属性名 id
writer.WriteValue("1");//id属性值为1
writer.WriteEndAttribute();//结束属性编写
writer.WriteStartElement("author");//作者子节点
writer.WriteString("刘晓飞");//作者子节点内容
writer.WriteEndElement();//结束作者子节点
writer.WriteEndElement();//结束book子节点

writer.WriteStartElement("book");//book子节点
writer.WriteStartElement("author");//作者子节点
writer.WriteString("张东");//作者节点内容
writer.WriteEndElement();//结束作者子节点
writer.WriteEndElement();//结束book子节点

writer.WriteEndDocument();//结束主节点

}
}