1.从数据库中取数据，使用DataSet对象创建XML文档

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.sqlClient;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender,EventArgs e)
    {
        String conStr = "Data Source=localhost;Initial Catalog=db_ks;uid=sa;password=sa123";
        sqlConnection myConn = new sqlConnection(conStr);//创建连接
        myConn.Open();//打开连接

        string cmdText = "select * from ks";//查询文本
        sqlDataAdapter da = new sqlDataAdapter(cmdText,myConn);//创建数据适配器实例对象

        DataSet ds = new DataSet();//创建数据集实例
        da.Fill(ds,"ks");//填充

        ds.WriteXml(Server.MapPath("App_Data/ks.xml"));//写入xml文件
        Response.Write("已经将ks表写入到ks.xml,位于App_Data里");
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Xml;

public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender,EventArgs e)
    {
        XmlTextWriter xmlTW = null;//创建XmlTextWriter对象的实例
        xmlTW = new XmlTextWriter(Server.MapPath("App_Data/books.xml"),null);
        xmlTW.Formatting = Formatting.Indented;//设置缩进格式
        xmlTW.Indentation = 3; //层次，可去
        xmlTW.WriteStartDocument();//文件头信息
        xmlTW.WriteComment("创建日期：" + DateTime.Now);//创建注释
        xmlTW.WriteStartElement("books");//根节点开始
        //节点开始
        xmlTW.WriteStartElement("book");
        xmlTW.WriteAttributeString("Category","技术类");//属性
        int intPageCount = 435;
        xmlTW.WriteAttributeString("PageCount",intPageCount.ToString("G"));
        xmlTW.WriteElementString("Title","ASP.NET动态网站开发教程");//元素
        //子节点开始
        xmlTW.WriteStartElement("AuthorList");
            xmlTW.WriteElementString("Author","张平");
            xmlTW.WriteElementString("Author","李澜");
        xmlTW.WriteEndElement();
        //子节点结束
        xmlTW.WriteEndElement();
        //结点结束

        //另一个节点开始
        xmlTW.WriteStartElement("book");
        xmlTW.WriteAttributeString("Category","文学类");//属性
        intPageCount = 500;
        xmlTW.WriteAttributeString("PageCount","青春赞歌");//元素
        //子节点开始
        xmlTW.WriteStartElement("AuthorList");
        xmlTW.WriteElementString("Author","陈明");
        xmlTW.WriteElementString("Author","王小虎");
        xmlTW.WriteEndElement();
        //子节点结束
        xmlTW.WriteEndElement();
        //另一结点结束

        xmlTW.WriteEndElement();//根节点结束
        xmlTW.Flush();//写入xml文档
        xmlTW.Close();//关闭
        Response.Write("xml文档已经生成");
    }
}