how to use cascading dropdownlist in mvc - asp.net-mvc-3

Question

am using asp.net mvc3, i have 2 tables in that i want to get data from dropdown based on this another dropdown has to perform.for example if i select country it has to show states belonging to that country,am using the following code in the controller.
ViewBag.country= new SelectList(db.country, "ID", "Name", "--Select--");
ViewBag.state= new SelectList("", "stateID", "Name");
#Html.DropDownListFor(model => model.Country, (IEnumerable<SelectListItem>)ViewBag.country, "-Select-")
#Html.DropDownListFor(model => model.state, (IEnumerable<SelectListItem>)ViewBag.state, "-Select-")
but by using this am able to get only the countries.

Answer 1

There is a good jQuery plugin that can help with this...
You don't want to refresh the whole page everytime someone changes the country drop down - an ajax call to simply update the state drop down is far more user-friendly.

Answer 2

Jquery Ajax is the best Option for these kind of questions.
Script Code Is Given below
<script type="text/javascript">
$(function() {
$("##Html.FieldIdFor(model => model.Country)").change(function() {
var selectedItem = $(this).val();
var ddlStates = $("##Html.FieldIdFor(model => model.state)");
$.ajax({
cache:false,
type: "GET",
url: "#(Url.Action("GetStatesByCountryId", "Country"))",
data: "countryId=" ,
success: function (data) {
ddlStates.html('');
$.each(data, function(id, option) {
ddlStates.append($('<option></option>').val(option.id).html(option.name));//Append all states to state dropdown through returned result
});
statesProgress.hide();
},
error:function (xhr, ajaxOptions, thrownError){
alert('Failed to retrieve states.');
statesProgress.hide();
}
});
});
});
</script>
Controller:
public ActionResult GetStatesByCountryId(string countryId)
{
// This action method gets called via an ajax request
if (String.IsNullOrEmpty(countryId))
throw new ArgumentNullException("countryId");
var country = GetCountryById(Convert.ToInt32(countryId));
var states = country != null ? GetStatesByConutryId(country.Id).ToList() : new List<StateProvince>();//Get all states by countryid
var result = (from s in states
select new { id = s.Id, name = s.Name }).ToList();
return Json(result, JsonRequestBehavior.AllowGet);
}

Answer 3

Try this,
<script type="text/javascript">
$(document).ready(function () {
$("#Country").change(function () {
var Id = $("#Country").val();
$.ajax({
url: '#Url.Action("GetCustomerNameWithId", "Test")',
type: "Post",
data: { Country: Id },
success: function (listItems) {
var STSelectBox = jQuery('#state');
STSelectBox.empty();
if (listItems.length > 0) {
for (var i = 0; i < listItems.length; i++) {
if (i == 0) {
STSelectBox.append('<option value="' + i + '">--Select--</option>');
}
STSelectBox.append('<option value="' + listItems[i].Value + '">' + listItems[i].Text + '</option>');
}
}
else {
for (var i = 0; i < listItems.length; i++) {
STSelectBox.append('<option value="' + listItems[i].Value + '">' + listItems[i].Text + '</option>');
}
}
}
});
});
});
</script>
View
#Html.DropDownList("Country", (SelectList)ViewBag.country, "--Select--")
#Html.DropDownList("state", new SelectList(Enumerable.Empty<SelectListItem>(), "Value", "Text"), "-- Select --")
Controller
public JsonResult GetCustomerNameWithId(string Country)
{
int _Country = 0;
int.TryParse(Country, out _Country);
var listItems = GetCustomerNameId(_Country).Select(s => new SelectListItem { Value = s.CountryID.ToString(), Text = s.CountryName }).ToList<SelectListItem>();
return Json(listItems, JsonRequestBehavior.AllowGet);
}