public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            var db = new SpeakerContext();
            var speakers = db.Speakers.ToList();

            filterContext.Controller.ViewData.Model = speakers;
        }
        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            var db = new SpeakerContext();
            var speakers = db.Speakers.Where(s => s.FirstName.StartsWith("A")).ToList();

            filterContext.Controller.ViewData.Model = speakers;
        }