public class CheckinLoginAttribute:ActionFilterAttribute 
 { 
 public override void OnActionExecuting(ActionExecutingContext filterContext) 
 { 
 if (filterContext.HttpContext.Session["user"] == null) 
 { 
 filterContext.HttpContext.Response.Redirect("/User/Login"); 
 } 
 } 
 }

public class HomeController : Controller 
 { 
 // 
 // GET: /Home/ 
 
 [CheckinLogin] 
 public ActionResult Index() 
 { 
 return View(); 
 } 
 
 }