after clicking submit button autocomplete textbox should not be empty in MVC3

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ASP.NET

MVC

mvc3 textbox retaining after button click.

my view code.

States Filter :

@Html.TextBox("Statestxt")
<input type="image" value="submit" src="../../Images/FilterBrowse.gif" alt="submit Button" />

My controller:

public ActionResult AutocompleteAsync(string term)
{
    var suggestions = from s in Adm.states
    select s.state_name;
    var namelist = suggestions.Where(n => n.ToLower().StartsWith(term.ToLower()));
    return Json(namelist, JsonRequestBehavior.AllowGet);
}

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult States(state stateModel, string _stateName, FormCollection formvalues)
{
    AdmDataContext Adm  = new AdmDataContext;
    if (Request.Form["Statestxt"] == null)
    {
        ViewBag.Error = "Enter State Name.";
        ViewData["name"] = false;
        return View();
    }
    else
    {
         _stateName = Request.Form["Statestxt"].ToString();
         var record = (from state in Adm.states
                                  where state.state_name == _stateName
                                  select state).Count();

         if (record == 0)
         {
             ViewBag.Error = "Enter Valid State Name.";
             return View();
         }

         var _Stateid = from state in Adm.states
                                  where state.state_name == _stateName
                                  select state;

         int StateId = (int)_Stateid.First().state_id;
         var state1 = am.FindUpcomingStates2(StateId).ToList();
         if (state1 != null)
         {
               ViewData["name"] = true;
               return View("States", state1);
         }
     }
}

Here after clicking submit button textbox is going to empty. How can i write code for textbox should not be empty.

Thanks.