How to Bind Drpdownlist's in Asp.Net MVC 4

@{
 ViewBag.Title = "Main";
}
<script type="text/javascript" src="../../Scripts/jquery-1.7.1.min.js"></script>
<script type="text/javascript">
    function GetState() { 
    var selectedValue = $('#ddlCountry').val();
        window.location.href = '/Bind/GetStatesByID/?countryCode=' + selectedValue;
    }
</script>
<h2>Main</h2>
@using (Html.BeginForm())
{

    @Html.DropDownList("Country", (SelectList)ViewBag.countryList, "--Choose Your Country--", new { id = "ddlCountry",onchange="GetState();" })
    @Html.DropDownList("State", (SelectList)ViewBag.stateList, "--Choose Your State--", new { id = "ddlState" })
}

public class BindController : Controller
   {
       //
       // GET: /Bind/

       public ActionResult Index()
       {
           ViewBag.countryList = GetAllCountrys();
           ViewBag.stateList = GetAllStates();
          return View("Main");
       }
       public ActionResult GetStatesByID(int? countryCode)
       {
           ViewBag.stateList = GetAllStatsByID(countryCode);
           ViewBag.countryList = new SelectList(GetAllCountrys(), "Value", "Text", countryCode);
           return View("Main");
       }

       private SelectList GetAllStatsByID(int? countryCode)
       {
           Data.TestEntities entity = new Data.TestEntities();
           {
               IEnumerable<SelectListItem> selectedStates = entity.States.Where(s => s.CountryID == countryCode).AsEnumerable().Select(m => new SelectListItem()
               {
                   Text = m.StateName
                   ,
                   Value = m.StateID.ToString()
               });
               return new SelectList(selectedStates, "Value", "Text", "--Select State--");
           }
       }
       private SelectList GetAllCountrys()
       {
           Data.TestEntities entity = new Data.TestEntities();
           {
               IEnumerable<SelectListItem> country = entity.Countries.AsEnumerable().Select(m => new SelectListItem()
               {
                   Text = m.CountryName
                   ,
                   Value = m.CountryID.ToString()
               });
               return new SelectList(country, "Value", "Text","--Select Country--");
           }

       }

       private SelectList GetAllStates()
       {
           Data.TestEntities entity = new Data.TestEntities();
           {
               IEnumerable<SelectListItem> states = entity.States.AsEnumerable().Select(m => new SelectListItem()
               {
                   Text = m.StateName
                   ,
                   Value = m.StateID.ToString()
               });
               return new SelectList(states, "Value", "Text", "--Select States--");
           }
       }
   }