Load Country/State/City

I have chain of drop down like Country / state and City. Is there is any way to wait until the drop down population th开发者_StackOverflowen proceed further? like first load the country and then based on the select of an country then load the state and same as city....

function populateLists(listType) {
    // on success do this:
    $.ajax({
    type:"POST",
    url:"Wizard_Using_PageMethod.aspx/GetCountry",
    data: "{}",
    contentType: "application/json; charset=utf-8",
    dataType:"json"}
});

[WebMethod]
public static CountryList GetCountry()
{
    CountryList country = new CountryList();
    ///go to db and get the data
    return country;
}

---

You may do like this

$('#cb_country').change(function(){
    var id=$(this).val();
    $.get('getCity.php',{id:id},function(data){
        $("#cb_city").html(data);
    });
});

getCity.php:

<?php
require('../conn.php');

$id=$_GET['id'];
$Q=mysql_query("SELECT * FROM city WHERE CountryID='".$id."' ORDER BY Cityname ASC");

do{
    echo "<option value='".$row['CityID']."'>".$row['CityName']."</option>";
}
while($row=mysql_fetch_assoc($Q));