web2.0时代 用Asp.Net写Rss，你会了吗？

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>