Filter records with dropdownlist

Good morning comrades I am trying to filter the records by means of a dropdownlist but at the moment of clicking the button it only refreshes the page but does not do any search.

controller

    public ViewResult Index(string estado, int? page)
        {

var estados = db.Representantes.OrderBy(p => p.EstadosT.Name).Select(p => p.EstadosT.Name).Distinct();

                if (!String.IsNullOrEmpty(estado))
                {
                   representante = db.Representantes.Where(s => s.EstadosT.Name.Contains(estado));

                }

                ViewBag.EstadosT = new SelectList( estados);
     return View(representante .ToList().ToPagedList(pageNumber, pageSize));
            }

view

@using (Html.BeginForm ()) {

    States: @ Html.DropDownList ("StatesT", "All")         

}