Body1.Attributes("bgcolor")属性设置问题?

.aspx
没问题的代码
<%@ Page Language="C#" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">  protected void SubmitBtn_Click(object sender, EventArgs e)
  {
    Body.Attributes["bgcolor"] = ColorSelect.Value;
  }
</script><html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
  <title>HtmlGenericControl Example</title> 
</head><body id="Body" 
      runat="server">     <h3>HtmlGenericControl Example</h3>     <form id="form1" runat="server">
     <div>
       <br />
       Select a background color for the page: <br />
       <select id="ColorSelect" 
               runat="server">
           <option>White</option>
           <option>LightBlue</option>
           <option>LightGreen</option>
           <option>Yellow</option>
       </select>       <input type="submit" 
              runat="server" 
              value="Apply" 
              onserverclick="SubmitBtn_Click" id="Submit1" />
     </div>
     </form> </body>
 </html>--------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------
.aspx
报错的代码
错误名称:编译器错误消息: CS1928: “System.Web.UI.HtmlControls.HtmlGenericControl”不包含“Attributes”的定义，
并且最佳扩展方法重载“System.Xml.Linq.Extensions.Attributes(System.Collections.Generic.IEnumerable<System.Xml.Linq.XElement>
, System.Xml.Linq.XName)”的某些参数无效
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Test_Web1.aspx.cs" Inherits="Test_Web1" %><!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 id="Head1" runat="server">
    <title>1234567</title>
</head>
<body  id="Body1" runat="server">
    <form id="form1" runat="server">
    <div>
        <h3>2314677</h3>
        <h3> I love you !!</h3><p>
        <asp:Button ID="Button1" runat="server" Text="Button" onclick="Button1_Click" />
    </div>
    </form>
</body>
</html>
.csusing System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;public partial class Test_Web1 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Body1.Attributes("bgcolor") = "White";              //报错
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
      //  Body1.Attributes("bgcolor") = "White";
    }
}
为什么报错呀,如何解决?谢谢回答 菜鸟问题