How to pass parameter from action filter to controller using C# in ASP.Net MVC

    public class IsStudentValid : System.Web.Mvc.ActionFilterAttribute
    {
        public Int32 StudentId { get; set; }
        public string ReviewStatus { get; set; }
        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
           
             StudentId  = (Int32)filterContext.ActionParameters.SingleOrDefault(p =>  p.Key == "StudentId").Value;
          


            
            if (StudentId != 0)
            {
                var validresult = db.Students.Where(c => c.StudentId == StudentId )
                    .Select(
                   c => new IsStudentValid {
                  CourseId=c.CourseId
                  ReviewStatus=c.ReviewStatus
                   } ).ToArray();

                if (validresult.Count() == 0)
                {

                    filterContext.Result = new RedirectToRouteResult(
                        new RouteValueDictionary{{ "controller", "Admin" },
                                          { "action", "Login" }
 
                                         });
                }
            }
            base.OnActionExecuting(filterContext);
        }
    }

i have the above custom filter

but its not working properly 

when i execute it first time i get all proper 

but after changing the id in url when i try to run again it goes thr' the above code but i get error in razon view file as system.nullexception

the above attribute is not working properly