小高分求助，关于HttpWebResponse 返回

用C#做一个模拟登陆页面，不能返会响应后的页面
 String loginUrl = "http://localhost/yh/admin/login.asp";
 CookieContainer session = new CookieContainer();
 
 public void getLoginPage()
        {
            string strUsername = tb_username.Text.Trim();
            string strPassword = tb_password.Text.Trim();            ASCIIEncoding encoding = new ASCIIEncoding();
            string postData = "username=" + strUsername;
            postData += ("&password=" + strPassword);            //postData = "username=steve&password=123456a%mofei=7049&submit=%C8%B7+%B6%A8";            byte[] data = encoding.GetBytes(postData);            // Prepare web request...   
            HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(loginUrl);                             myRequest.CookieContainer = session;            myRequest.Method = "POST";
            myRequest.ContentType = "application/x-www-form-urlencoded";
            myRequest.ContentLength = data.Length;
            Stream newStream = myRequest.GetRequestStream();            
            // Send the data.   
            newStream.Write(data, 0, data.Length);       
            newStream.Close();            // Get response   
            HttpWebResponse myResponse = (HttpWebResponse)myRequest.GetResponse();
            StreamReader reader = new StreamReader(myResponse.GetResponseStream(), Encoding.Default);
            string content = reader.ReadToEnd();            richTextBox1.Text = richTextBox1.Text + content;
        }
login.asp<!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>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
</head><form name="form1" method="post" action="login_chk.asp">
<table>
    <tr>
      <td height="30"  colspan="2" align="center" bgcolor="#E8E8E8" class="td_2"><b>管理登陆</b></td>
    </tr>
    <tr>
      <td width="80" align="center" class="td_2">用户名： </td>
      <td width="220" class="td_2"><input type="text" name="username" class="input1" size="19"></td>
    </tr>
    <tr>
      <td align="center" class="td_2">密&nbsp;&nbsp;码：</td>
      <td class="td_2"><input type="password" name="password" class="input1" size="19"></td>
    </tr>  
    <tr>
      <td height="30" colspan="2" align="center" valign="middle" class="td_2"><input style="color: #FFFFFF; background-color: #FF1171; border: 1px solid #000000" type="submit" value="确 定" name="Submit">
&nbsp;&nbsp;&nbsp;
      <input style="color: #FFFFFF; background-color: #FF1171; border: 1px solid #000000" type="reset" value="取 消" name="Submit2"></td>
    </tr>
</table>
  </form><body>
</body>
</html>
login_chk.asp<%
if Request("username") ="1" and Request("password") = "1" then
Response.Write("用户登陆成功")
else
Response.Write ("请输入正确的用户名和密码")
end if
%>