DropdownList AutoPostback Functionality In MVC Using C#.Net

This article will show you how you can make dropdownlist autopostback functionality in asp.net mvc using c#.net.  This article you can use MVC3/MVC4/MVC5/MVC6.

Some of my previous articles are as follows: XML File Generation And Data Writing Using C#.Net In Asp.Net MVC, How To Read XML File in DataTable Using C#.Net In Asp.Net MVC, Cookies Create, Read and Delete Operation Using jQuery in Asp.Net, Bind XML File Data to Gridview By Category and SubCategory in Asp.Net MVC Using C#.Net, MVC Pass Multiple Parameters in QueryString or URL in Asp.Net MVC, jQuery Ajax Search and Display In MVC WebGrid in Asp.Net MVC Using C#.Net, Search and Display Data In MVC WebGrid in Asp.Net MVC Using C#.Net, Bind WebGrid With Entity Framework in Asp.Net MVC Using C#.Net.

So for this article first we will create a new asp.net mvc application and add a model class file and add the below code.

using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; namespace MvcApplication1.Models {     public class StateModel     {         public int StateId { get; set; }         public SelectList StateList { get; set; }         public List<City> CityList { get; set; }     }     public class City     {         public int CityId { get; set; }         public int StateId { get; set; }         public string CityName { get; set; }     } }

Now add controller class and the below code.

using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; using MvcApplication1.Models; namespace MvcApplication1.Controllers {     public class HomeController : Controller     {         public ActionResult Index()         {             StateModel objStateModel = new StateModel();             objStateModel.StateList = State();             List<City> objcity = new List<City>();             objcity = GetCityList(0);             objStateModel.CityList = objcity;             return View(objStateModel);         }         [HttpPost]         public ActionResult Index(int StateId)         {             StateModel objStateModel = new StateModel();             objStateModel.StateList = State();             List<City> objcity = new List<City>();             objcity = GetCityList(StateId);             objStateModel.CityList = objcity;             return View(objStateModel);         }         public SelectList State()         {             List<SelectListItem> items = new List<SelectListItem>();             items.Add(new SelectListItem() { Text = "State 1", Value = "1", Selected = true });             items.Add(new SelectListItem() { Text = "State 2", Value = "2", Selected = false });             SelectList objstatelist = new SelectList(items, "Value", "Text", 0);             return objstatelist;         }         public List<City> GetCityList(int stateID)         {             List<City> objCity = new List<City>();             objCity.Add(new City { CityId = 1, StateId = 1, CityName = "City 1" });             objCity.Add(new City { CityId = 2, StateId = 2, CityName = "City 2" });             objCity.Add(new City { CityId = 3, StateId = 1, CityName = "City 3" });             return objCity.Where(m => m.StateId == stateID).ToList();         }     } }

Now create view and add the below code into view page.

@model MvcApplication1.Models.StateModel @{     ViewBag.Title = "DropdownList AutoPostback Functionality In MVC Using C#.Net"; } @using (Html.BeginForm("Index", "Home")) {     @Html.DropDownListFor(model => model.StateId, new SelectList(Model.StateList, "Value", "Text"), new { @onchange = "this.form.submit();" })     <br />     <br />     <div>       <b>  CITY AS PER STATE</b></div>     foreach (var item in Model.CityList)     {     <div>         <b>City Name :</b>@item.CityName</div>     } }

Now run the page to check the output.