.net 里面有没有EL表达式啊...............

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;public partial class detailNews : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
     string url=Request.QueryString["url"];
    
    }
}
html:<%@ Page Language="C#" AutoEventWireup="true" CodeFile="detailNews.aspx.cs" Inherits="detailNews" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>无标题页</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
      <iframe src="<% Eval("url") %>"></iframe>
    </div>
    </form>
</body>
</html>
怎么获取url的值啊？[b][/b]