public override void Application_BeginRequest(object sender, EventArgs e)
{
HttpContext.Current.Response.AppendHeader("Pragma", "no-cache");
HttpContext.Current.Response.AppendHeader("Cache-Control", "no-cache");
HttpContext.Current.Response.CacheControl = "no-cache";
HttpContext.Current.Response.Expires = -1;
HttpContext.Current.Response.ExpiresAbsolute = new DateTime(1900, 1, 1);
HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
}