In the previous article, we have discussed How to get data from database using JQuery Ajax in asp net MVC, In This article, we will discuss how to create MVC Cascading Dropdown using JQuery AJAX i.e we will cascade one dropdown list with another dropdown list in ASP.Net MVC using JQuery AJAX. In this article, we will take 3 dropdown lists, Organization, Employees, and Employee_address.

We will see how to fill the Employees dropdown list based on the data of the Organization dropdown list and then the Employee_address dropdown list based on the selected Employees.

Step 1: Create Database Table

Let’s create the database table for our task, for cascading dropdownlist in asp.net MVC using jquery ajax. I have created 3 tables called “Organization” with column Id, Name. “Employees” with [Id],[Name] ,[Salary],[OrganizationId] and Employee_address with column [Id],[Address],[City],[ZipCode],[EmployeeId].
You can find the SQL Script of the table below.

/****** Object:  Table [dbo].[Employee_address]    Script Date: 2/11/2022 2:51:52 PM ******/
CREATE TABLE [dbo].[Employee_address](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Address] [nvarchar](50) NULL,
    [City] [nvarchar](50) NULL,
    [ZipCode] [int] NULL,
    [EmployeeId] [int] NULL,
 CONSTRAINT [PK_Departments] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
))
/****** Object:  Table [dbo].[Employees]    Script Date: 2/11/2022 2:51:52 PM ******/
CREATE TABLE [dbo].[Employees](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Name] [nvarchar](50) NULL,
    [Salary] [float] NULL,
    [OrganizationId] [int] NULL,
 CONSTRAINT [PK_Employees] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
) ON [PRIMARY])

/****** Object:  Table [dbo].[Organization]    Script Date: 2/11/2022 2:51:52 PM ******/
CREATE TABLE [dbo].[Organization](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [CompanyName] [nvarchar](50) NULL,
 CONSTRAINT [PK_Organization] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
))
GO
SET IDENTITY_INSERT [dbo].[Employee_address] ON 
GO
INSERT [dbo].[Employee_address] ([Id], [Address], [City], [ZipCode], [EmployeeId]) VALUES (1, '3899 Grey Fox Farm Road', 'Houston', 20120, 1)
GO
INSERT [dbo].[Employee_address] ([Id], [Address], [City], [ZipCode], [EmployeeId]) VALUES (2, '4790 Happy Hollow Road', 'Wilmington', 28405, 2)
GO
INSERT [dbo].[Employee_address] ([Id], [Address], [City], [ZipCode], [EmployeeId]) VALUES (3, '742 Arbutus Drive', 'Miami', 33145, 3)
GO
INSERT [dbo].[Employee_address] ([Id], [Address], [City], [ZipCode], [EmployeeId]) VALUES (4, '1852 Willow Greene Drive', 'Montgomery', 5522, 4)
GO
INSERT [dbo].[Employee_address] ([Id], [Address], [City], [ZipCode], [EmployeeId]) VALUES (5, '7742 Arbutus Drive', 'Miami', 33145, 5)
GO
INSERT [dbo].[Employee_address] ([Id], [Address], [City], [ZipCode], [EmployeeId]) VALUES (6, '742 Drive', 'Miami', 33145, 6)
GO
SET IDENTITY_INSERT [dbo].[Employee_address] OFF
GO
SET IDENTITY_INSERT [dbo].[Employees] ON 
GO
INSERT [dbo].[Employees] ([Id], [Name], [Salary], [OrganizationId]) VALUES (1, 'Mark', 6000, 1)
GO
INSERT [dbo].[Employees] ([Id], [Name], [Salary], [OrganizationId]) VALUES (2, 'Henry', 3000, 1)
GO
INSERT [dbo].[Employees] ([Id], [Name], [Salary], [OrganizationId]) VALUES (3, 'Thomas', 4000, 2)
GO
INSERT [dbo].[Employees] ([Id], [Name], [Salary], [OrganizationId]) VALUES (4, 'Jack', 6000, 2)
GO
INSERT [dbo].[Employees] ([Id], [Name], [Salary], [OrganizationId]) VALUES (5, 'Tim', 5000, 3)
GO
INSERT [dbo].[Employees] ([Id], [Name], [Salary], [OrganizationId]) VALUES (6, 'Luis', 4000, 3)
GO
INSERT [dbo].[Employees] ([Id], [Name], [Salary], [OrganizationId]) VALUES (7, 'Southy', 6000, 3)
GO
SET IDENTITY_INSERT [dbo].[Employees] OFF
GO
SET IDENTITY_INSERT [dbo].[Organization] ON 
GO
INSERT [dbo].[Organization] ([Id], [CompanyName]) VALUES (1, 'Microsoft')
GO
INSERT [dbo].[Organization] ([Id], [CompanyName]) VALUES (2, 'Google')
GO
INSERT [dbo].[Organization] ([Id], [CompanyName]) VALUES (3, 'Apple')
GO
SET IDENTITY_INSERT [dbo].[Organization] OFF
GO
ALTER TABLE [dbo].[Employee_address]  WITH CHECK ADD  CONSTRAINT [FK_Departments_Employees] FOREIGN KEY([EmployeeId])
REFERENCES [dbo].[Employees] ([Id])
GO
ALTER TABLE [dbo].[Employee_address] CHECK CONSTRAINT [FK_Departments_Employees]
GO
ALTER TABLE [dbo].[Employees]  WITH CHECK ADD  CONSTRAINT [FK_Employees_Organization] FOREIGN KEY([OrganizationId])
REFERENCES [dbo].[Organization] ([Id])
GO
ALTER TABLE [dbo].[Employees] CHECK CONSTRAINT [FK_Employees_Organization]
GO

Step 2 :Open your VS19 or VS22, create an empty MVC website if don’t know how to create an empty project then please read below basic crud operation article.

Step 3 : we are  using Entity Framework for Cascading dropdown

In Model Folder, right-click then select Add New Item -> Data option on the left side menu. select ADO .net entity framework.
and follow the below step.

Step 4: Adding HomeController in our project
Now let’s add a Homecontroller in our project for showing the list, Right-click on the Controller folder in the project =>add an empty controller.

Now open Homecontroller.cs and let’s write the code in our controller, and add the following action methods. Here, I am going to add one action method to our controller which returns all Index view.

Homecontroller.cs

using Cascading.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace Cascading.Controllers
{
    public class HomeController : Controller
    {
        DemoDatabaseEntities context = new DemoDatabaseEntities();
        // GET: Home
        public ActionResult Index()
        {
            var Organizations = context.Organizations.ToList();
            return View(Organizations);
        }

        //retrun all employee by OrganizationsId
        [HttpPost]
        public JsonResult GetEmployeedByOrganizationIdId(int OrganizationId)
        {
            var Employees = (from r in context.Employees
                          where r.OrganizationId == OrganizationId
                          select new
                          {
                              r.Id,
                              r.Name
                          }).ToList();
            return Json(Employees, JsonRequestBehavior.AllowGet);
        }
        //return all employee address because a employee can have multiple address
        [HttpPost]
        public JsonResult GetEmployeeAddressBydId(int EmployeeId)
        {
            var EmployeesAddress = (from r in context.Employee_address
                             where r.EmployeeId == EmployeeId
                             select new
                             {
                                 r.Id,
                                 r.Address
                             }).ToList();
            return Json(EmployeesAddress, JsonRequestBehavior.AllowGet);
        }
    }
}

Step 5: Create copy paste the below code in Index.cshtml view

@model IEnumerable<Cascading.Models.Organization>
@{
    ViewBag.Title = "Index";
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<h2>Cascading Dropdownlist Example</h2>
<div>
    <label>Organizations</label>
    <select id="ddlOrganization" onchange="LoadEmployees()">
        <option>Select Organization</option>
        @if (Model != null && Model.Count() > 0)
        {
            foreach (var item in Model)
            {
                <option value="@item.Id">@item.CompanyName</option>
            }
        }
    </select>
    <br />
    <br />
    <label>Employees</label>
    <select id="ddlEmployees" onchange="LoadEmployeesAddress()">
    </select>
    <br />
    <br />
    <label>Employees Address</label>
    <select id="ddlAddress">
    </select>
</div>
<script type="text/javascript">
    function LoadEmployees()
    {
        var OrzanId = $("#ddlOrganization").val();
        if (OrzanId) {
            $.ajax({
                type: "POST",
                url: "/Home/GetEmployeedByOrganizationIdId",
                data: { OrganizationId: OrzanId},
                success: function (empdata) {
                    var ddlEmployees = $("#ddlEmployees");
                    ddlEmployees.empty()
                    $("#ddlAddress").empty();
                    if (empdata) {
                        ddlEmployees.append($('<option/>', {
                            value: 0,
                            text: "Select a employees"
                        }));
                        $.each(empdata, function (index, empData) {
                            ddlEmployees.append($('<option/>', {
                                value: empData.Id,
                                text: empData.Name
                            }));
                        });
                    }
                }
                ,
                error: function (ex) {
                    alert(ex);
                }
            });
        }
    }


    function LoadEmployeesAddress() {
        var EmployeesId = $("#ddlEmployees").val();
        if (EmployeesId) {
            $.ajax({
                type: "POST",
                url: "/Home/GetEmployeeAddressBydId",
                data: { EmployeeId: EmployeesId },
                success: function (empaddressdata) {
                    var ddlAddress = $("#ddlAddress");
                    ddlAddress.empty()
                    if (empaddressdata) {
                        $.each(empaddressdata, function (index, empaddData) {
                            ddlAddress.append($('<option/>', {
                                value: empaddData.Id,
                                text: empaddData.Address
                            }));
                        });
                    }
                }
                ,
                error: function (ex) {
                    alert(ex);
                }
            });
        }
    }

</script>

Step:6 Build Run Project