Dropdownlist in asp.net mvc3

Question

Hi,
I am working on asp.net mvc3 using ado.net asynchronous concept
I have written country dropdown as following
<select name="" class="styled" id="countryDropDown"> 
  @foreach(var country in HttpContext.Current.Cache.Get("Countries") as  List<Country>)
  {
  <option value="@country.Id" >@country.Name</option>
  }
</select>

I have another two dropdownlists- statedropdown and citydropdown

I want to fill statedropdown based on countryId
I want to fill citydropdown based on stateId
My state controle action
public ActionResult GetStatesCompleted(IList<StateProvince> states)
  {
  //Up to here I am getting states list, what I have to write here for return states to view
  }
Can you anyone tell me how to write controle and view to do this

Thankyou for advance...