rss是站点与站点之间共享内容的一种简易方式(也称为“聚合内容”)，通常被用于新闻和其他按顺序排列的网站，例如blog网站。网站提供rss输出，有利于让用户发现网站内容的更新。网站用户可以在客户端借助于类似新闻资讯阅读器等支持rss的新闻聚合工具软件，在不打开网站内容页面的情况下阅读支持rss输出的网站内容。
     rss是基于xml的一种形式。并且所有的rss文件都要遵守万维网联盟(w3c)站点发布的xml 1.0规范。具体格式可以查一下rss 2.0规范，这里就不再重复粘贴了。

下面是我总结的几种rss的技术实现代码：

1.在线生成rss聚合页。

(1)创建rss.aspx
<%@ page language="c#" codebehind="rss.aspx.cs" autoeventwireup="false" inherits="litianping.rss" %>
只留下这一行，其余的都删掉。

(2)后台代码；rss.aspx.cs

  private void page_load(object sender, system.eventargs e)
  {    
   response.contenttype="text/xml";
   response.write(getrss());
  }

  /// <summary>
  /// 取得聚合文章
  /// </summary>
  /// <returns></returns>
  public string getrss()
  {
   news t=new news();//自己的业务类
   dataset ds=t.getlistbyclass(1);//根据类别得到数据
   
   stringbuilder strcode=new stringbuilder();
   strcode.append("<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\" ?>");
   strcode.append("<rss version=2.0 xmlns:dc=\"http://purl.org/dc/elements/1.1/\"");
   strcode.append(" xmlns:trackback=\"http://madskills.com/public/xml/rss/module/trackback/\" ");
   strcode.append(" xmlns:wfw=\"http://wellformedweb.org/commentapi/\" xmlns:slash=\"http://purl.org/rss/1.0/modules/slash/\">");
   strcode.append("<channel>");
   strcode.append("<title>李天平rssdemo</title>");
   strcode.append("<link>http://"+request.servervariables["server_name"]+"</link> ");
   strcode.append("<description>天道酬勤</description> ");  
   strcode.append("<copyright>copyright 2005</copyright> ");      
   
   foreach(datarow row in ds.tables[0].rows)
   {
    string id=row["id"].tostring();
    string title=row["title"].tostring();
    string description=row["description"].tostring();
    string pubdate=row["pubdate"].tostring();
    string classid=row["classid"].tostring();
    //string author=row["author"].tostring();

    strcode.append("<item>");
    strcode.append("<title>"+title+"</title>");
    strcode.append("<link>http://"+request.servervariables["server_name"]+"/newsshow.aspx?id="+id+"</link>");
    strcode.append("<subject>"+description+"</subject>");
    strcode.append("<description><![cdata["+description+"]]></description>");    
    strcode.append("<pubdate>"+pubdate+"</pubdate>");
    strcode.append("<category>"+classid+"</category>");
    strcode.append("</item>");    
   }
   strcode.append("</channel>");
   strcode.append("</rss>");  
   return strcode.tostring();
  }

 (3) xmltextwriter实现方式2；rss.aspx.cs

  string xmldoc="rss.xml"; 
 private void page_load(object sender, system.eventargs e)
  {    
   xmldoc=server.mappath(".")+xmldoc;   
   getrss2();
   xmldocument doc= new xmldocument();
   doc.load(xmldoc);
   response.contenttype = "text/xml";
   doc.save(response.output);
  }
  /// <summary>
  /// 取得聚合文章
  /// </summary>
  /// <returns></returns>
  public void getrss2()
  {
   news t=new news();
   dataset ds=t.getlistbyclass(1);
   
   xmltextwriter writer = new xmltextwriter(xmldoc,encoding.utf8);
   writer.formatting = formatting.indented;
   writer.writestartdocument(true);
   writer.writecomment("rss页的实现");
   writer.writestartelement("rss");
   writer.writeattributestring("version","2.0");      
   writer.writestartelement("channel");   
   writer.writestartelement("title");
   writer.writestring("李天平rssdemo");
   writer.writeendelement();
   writer.writestartelement("link");   
   writer.writestring("http://"+request.servervariables["server_name"]);
   writer.writeendelement();   
   writer.writestartelement("description");
   writer.writestring("天道酬勤");
   writer.writeendelement();
   writer.writestartelement("copyright");
   writer.writestring("copyright 2005");
   writer.writeendelement();
   writer.writestartelement("language");
   writer.writestring("zh-cn");
   writer.writeendelement();  
      
   foreach(datarow row in ds.tables[0].rows)
   {
    string id=row["id"].tostring();
    string title=row["title"].tostring();
    string description=row["description"].tostring();
    string pubdate=row["pubdate"].tostring();
    string classid=row["classid"].tostring();
    //string author=row["author"].tostring();

    writer.writestartelement("item");
    writer.writestartelement("title");
    writer.writestring(title);
    writer.writeendelement();
    writer.writestartelement("link");
    writer.writestring("http://"+request.servervariables["server_name"]+"/newsshow.aspx?id="+id) ;
    writer.writeendelement();
    writer.writestartelement("description");
    writer.writecdata(description);
    writer.writeendelement();
    writer.writestartelement("pubdate");
    writer.writestring(pubdate);
    writer.writeendelement();
    writer.writestartelement("category");
    writer.writestring(classid);
    writer.writeendelement();
    writer.writeendelement();  
   }
   writer.writeendelement();
   writer.writeendelement();
   writer.flush();
   writer.close();
 
  }
2.在线rss阅读获取。

页面代码：
  <p style="font-size: 11px">
   feed种子：<asp:textbox id="feedurl" runat="server" width="440px"></asp:textbox><br>
   显示条数：<asp:textbox id="num" runat="server" width="48px"></asp:textbox></p>
  <p style="font-size: 11px">
   <asp:button id="getfeed" runat="server" text="获得rss"></asp:button><br>
   <br>
   <asp:label id="rssfeed" runat="server"></asp:label></p>

后台代码：
  /// <summary>
  /// 获得要显示的feed种子数据
  /// </summary>
  /// <param name="rssurl"></param>
  /// <param name="shownewscount"></param>
  /// <returns></returns>
  public string loadrss(string rssurl, int shownewscount)
  {
   string strrsslist = "";
   string strmsg;
   try
   {      
    xmldocument objxmldoc = new xmldocument();   
    objxmldoc.load(rssurl);  
    xmlnodelist objitems = objxmldoc.getelementsbytagname("item");    
  
    if(shownewscount > 30)
     shownewscount = 10;  
    if(shownewscount < 1)
     shownewscount = objitems.count;
  
    string title="";
    string link=""; 
    int i;

    if(objxmldoc.haschildnodes == true)
    {
     i = 1;
        foreach(xmlnode objnode in objitems)
     {
      if(i<=shownewscount)
      {
       if(objnode.haschildnodes == true)
       {
        xmlnodelist objitemschild = objnode.childnodes;
        foreach(xmlnode objnodechild in objitemschild)
        {
         switch(objnodechild.name)
         {
          case "title":
           title = objnodechild.innertext;
           break;
          case "link":
           link = objnodechild.innertext;
           break;          
         }         
        }
        i = i+1;
        strrsslist += "<a href=" + link +" target=_blank>" + title + "</a><br>"; 
       }      
      }
     }       
    }
    strmsg = strrsslist;
   }
   catch
   {
    strmsg = "rss feed 源数据出错！";
   }
   return strmsg;
  }

  //获取按钮,获取指定rss
  private void getfeed_click(object sender, system.eventargs e)
  {
   if(feedurl.text == "")//rss地址
   {
    rssfeed.text = "信息源不能为空，您可刷新重试或联系管理员！";
    return ;
   }  
   rssfeed.text = loadrss(feedurl.text,convert.toint32(num.text)); //获取指定数目 
  }

3.无刷新动态更新的在线rss阅读获取

<%@ page language="c#" codebehind="xmlhttp.aspx.cs" autoeventwireup="false" inherits="litianping.xmlhttp" %>
<!doctype html public "-//w3c//dtd html 4.0 transitional//en" >
<html>
 <head>
  <title>xmlhttp</title>
  <meta name="generator" content="microsoft visual studio .net 7.1">
  <meta name="code_language" content="c#">
  <meta name="vs_defaultclientscript" content="javascript">
  <meta name="vs_targetschema" content="http://schemas.microsoft.com/intellisense/ie5">
  <style>td { font-size: 9pt}
  </style>
  <script>
  <!-- 
  var odiv
  var xh    
  function getxml()
  {   
   xh =new activexobject("microsoft.xmlhttp");
   odiv = document.getelementbyid("rssitem");
   odiv.style.display= "";
   try
   {
    //如果是本地改成下面语句直接读取
    //xh.open("get","/rss.aspx",false);    
    xh.open("get","http://ltp.cnblogs.com/rss.aspx",false);
    xh.send(null);
    loaddata(xh,odiv);
   }
   catch(e)
   {
    error(odiv);
   }
  }
  function loaddata(xh,odiv)
  {
   if (xh.readystate == 4)
   {
    xml = xh.responsexml;
    var i;
    var nodes = xml.selectnodes("/rss/channel/item");
    var bloglink = xml.selectsinglenode("/rss/channel/link").text;
    odiv.innerhtml = "";
    var html;    
    for(i=0;i<nodes.length;i++)
    {    
        
      html += "<div >";
      html += "    <div >";
      html += "        <a class=font1 href=" +nodes[i].selectsinglenode("link").text + " target=_blank>" + nodes[i].selectsinglenode("title").text +"</a><br><br>";
      html += "    </div>";
      html += "    <div >";
      html += "        " +nodes[i].selectsinglenode("description").text;
      html += "    </div>"           
      //html += "    </div>";
      html += "</div><hr>";

    }
    odiv.innerhtml = html;
   }
   else
   {
    error(odiv);
   }
  }

  function error(odiv)
  {
   odiv.innerhtml = "载入失败";
  }
  -->
  </script>
 </head>
 <body ms_positioning="gridlayout" onload="window.settimeout(getxml(),200);">
  <form id="form1" method="post" runat="server">
   <div align=center>
   <table cellpadding="0" cellspacing="0" border="0" width="80%">
    <tr>
     <td>
      <div id="rssitem" style="width:80%">数据载入中...</div>
     </td>
    </tr>
   </table>
   </div>
  </form>
 </body>
</html> （作者：李天平    转载请注明）