Preselect the list items in multiple cascading DropDownList

12 Apr 20224 minutes to read

CSHTML

<div class="padding-top">

    @Html.EJS().DropDownList("country").Placeholder("Select a country").PopupHeight(@ViewBag.popupHeight).Change("countrychange").DataSource((IEnumerable<Object>)ViewBag.country).Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings { Text = "CountryName", Value = "CountryId" }).Render()
</div>
<div class="padding-top">

    @Html.EJS().DropDownList("state").Placeholder("Select a state").Enabled(false).PopupHeight(ViewBag.popupHeight).Change("statechange").DataSource((IEnumerable<Object>)ViewBag.state).Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings { Text = "StateName", Value = "StateId" }).Render()
</div>
<div class="padding-top">

    @Html.EJS().DropDownList("city").Placeholder("Select a city").Enabled(false).PopupHeight(ViewBag.popupHeight).DataSource((IEnumerable<Object>)ViewBag.cities).Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings { Text = "CityName", Value = "CityId" }).Render()
</div>

<script type="text/javascript">
    function countrychange() {
        // disable the state DropDownList
        var countryObj = document.getElementById('country').ej2_instances[0];
        var state = document.getElementById('state').ej2_instances[0];
        var city = document.getElementById('city').ej2_instances[0];
        state.enabled = true;
        //frame the query based on selected value in country DropDownList.
        var tempQuery = new ej.data.Query().where('CountryId', 'equal', countryObj.value);
        // set the framed query based on selected value in country DropDownList.
        state.query = tempQuery;
        // set null value to state DropDownList text property
        state.text = null;
        //  bind the property changes to state DropDownList
        state.dataBind();
        // set null value to city DropDownList text property
        city.text = null;
        // disable the city DropDownList
        city.enabled = false;
        // bind the property changes to City DropDownList
        city.dataBind();
    }
    function statechange() {
        var stateObj = document.getElementById('state').ej2_instances[0];
        var city = document.getElementById('city').ej2_instances[0];
        city.enabled = true;
        //Query the data source based on state DropDownList selected value
        var tempQuery = new ej.data.Query().where('StateId', 'equal', stateObj.value);
        //set the framed query based on selected value in city DropDownList.
        city.query = tempQuery;
        //clear the existing selection
        city.text = null;
        //bind the property change to city DropDownList
        city.dataBind();

    }
</script>

Country.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace WebApplication1.Models
{
    public class Country
    {
        public string CountryName { get; set; }
        public string CountryId { get; set; }

        public List<Country> CountryList()
        {
            List<Country> country = new List<Country>();
            country.Add(new Country() { CountryName = "Australia", CountryId = "2" });
            country.Add(new Country() { CountryName = "United States", CountryId = "1" });
            return country;
        }
    }
}