cascadingdropdownone.cs

public ActionResult Index()
{
    continents = new List();
    continents.Add(new SelectListItem { Text = "Select continent", Value = "0" });
    continents.Add(new SelectListItem { Text = "Europe", Value = "1" });
    continents.Add(new SelectListItem { Text = "North America", Value = "2" });
    continents.Add(new SelectListItem { Text = "South America", Value = "3" });
    ViewData["continents"] = continents;

    countries = new List();
    countries.Add(new SelectListItem { Text = "Select country", Value = "0" });
    ViewData["countries"] = countries;

    cities = new List();
    cities.Add(new SelectListItem { Text = "Select city", Value = "0" });
    ViewData["cities"] = cities;

    return View();
}