public double time;
public const int freetime = 1;//防刷冰冻时间间隔,当前为1秒

#region 防恶意刷新
if (Session.SessionID == null)
{
  Response.End();
}
else if (Session["sionid"] == null)
{
  Session["sionid"] = Session.SessionID;
}
if (Session["last"] == null)
{
  Session["last"] = DateTime.Now;
}
else
{
  DateTime thisTime = DateTime.Now;
  DateTime lastTime = DateTime.Parse(Session["last"].ToString());

  if (Session.SessionID == Session["sionid"].ToString())
 Session["last"] = thisTime;
  TimeSpan ts = thisTime - lastTime;

  time = ts.TotalMilliseconds;
  if (time < freetime * 500)
  {
 warm_prompt();
  }
}
#endregion

public void warm_prompt()
{
    Response.Write("<table width='778' border='0' align='center' cellpadding='3' cellspacing='2' bgcolor='#009900' style='font-size: 14px; '>");
    Response.Write(" <tr bgcolor='#FFFFFF'>");
    Response.Write("  <td><img src='/newimages/logos.gif'></td>");
    Response.Write("  <td bgcolor='#EEFFEE'为了保证您的访问安全,请您 " + freetime + " 秒后<a href='" + Request.RawUrl + "' target='_self' style='color:#FF0000;'>点击这里刷新</a>此页面</td>");
    Response.Write(" </tr>");
    Response.Write("</table>");
    Response.End();
}

public double time;
public const int freetime = 2;

#region 防恶意刷新
string page;
if (Request.Cookies["page"] == null)
{
  page = "";
}
else
{
  page = HttpContext.Current.Request.Cookies["page"].Value.ToString(); //获取cookie中存储的url值 
}

string strThisPage = HttpContext.Current.Request.Url.PathAndQuery.ToString();//获取当前页地址 
DateTime LastTime = DateTime.Now;
if (page.Equals(strThisPage))//如果cookie中的值和当前页相等，那么表示是刷新操作 
{
  TimeSpan ts = LastTime - DateTime.Parse(HttpContext.Current.Request.Cookies["time"].Value.ToString());

  time = ts.Seconds;
  if (time < freetime)
  {
 warm_prompt();
  }
}
else
{
  //执行操作 
  Response.Cookies["page"].Value = strThisPage;
  Response.Cookies["time"].Value = LastTime.ToString();
}
#endregion

public void warm_prompt()
{
    Response.Write("<table width='778' border='0' align='center' cellpadding='3' cellspacing='2' bgcolor='#009900' style='font-size: 14px; '>");
    Response.Write(" <tr bgcolor='#FFFFFF'>");
    Response.Write("  <td><img src='/newimages/logos.gif'></td>");
    Response.Write("  <td bgcolor='#EEFFEE'为了保证您的访问安全,页面将在2秒后将自动跳转到您要访问的内容！</td>");
    Response.Write(" </tr>");
    Response.Write("</table>");
    Response.Write("<meta http-equiv=\"refresh\" content=\"2\";URL=" + HttpContext.Current.Request.Cookies["page"].Value.ToString() + ">");
    Response.End();
}