ASPNet Core MVC Multiple Select MultiSelect DropDownList with CheckBoxes

In this article I will explain with an example, how to bind (populate) Multiple Select (Multi-Select) DropDownList with CheckBoxes from database using jQuery in ASP.Net Core (.Net Core 8) MVC.

The Multiple Select (Multi-Select) DropDownList with CheckBoxes will be implemented using jQuery Bootstrap Multi-Select plugin.

Note: For beginners in ASP.Net Core (.Net Core 8) MVC, please refer my article ASP.Net Core 8: Hello World Tutorial with Sample Program example.

Download Bootstrap and jQuery Bootstrap Multi-Select Plugin

The download locations are as follows.

Bootstrap

https://getbootstrap.com/

jQuery BoosStrap Multi-Select Plugin

You will need to download the plugin files from the following location.

https://github.com/davidstutz/bootstrap-multiselect/

The complete documentation can be read on the following page.

https://davidstutz.github.io/bootstrap-multiselect/

Database

I have made use of the following table Fruits with the schema as follows.

ASP.Net Core MVC: Multiple Select (Multi-Select) DropDownList with CheckBoxes

I have already inserted few records in the table.

Note: You can download the database table SQL by clicking the download link below.

Download SQL file

Model

The Model class consists of following properties.

The property FruitId is decorated with the following Data Annotation attributes:

Key – It is used to apply the Primary Key constraint to the Column.

using System.ComponentModel.DataAnnotations;

public class FruitModel

{

[Key]

public int FruitId { get; set; }

public string FruitName { get; set; }

}

Database Context

Once the Entity Framework is configured and connected to the database table, the Database Context will look as shown below.

Note: For beginners in ASP.Net Core (.Net Core 7) MVC and Entity Framework, please refer my article ASP.Net Core 7: Simple Entity Framework Tutorial with example. It covers all the information needed for connecting and configuring Entity Framework with ASP.Net Core (.Net Core 7) MVC.

using Microsoft.EntityFrameworkCore;

namespace CheckBox_DropDownList_MVC_Core

{

public class DBCtx : DbContext

{

public DBCtx(DbContextOptions<DBCtx> options) : base(options)

{

}

public DbSet<FruitModel> Fruits { get; set; }

}

Namespaces

You will need to import the following namespaces.

using System.Collections.Generic;

using Microsoft.AspNetCore.Mvc.Rendering;

Controller

The Controller consists of following Action methods.

Action method for handling GET operation

Inside this Action method, the PopulateFruits method is called.

Inside the PopulateFruits method, the records from the Fruits table are fetched using Entity Framework and are copied into generic list of SelectListItem class and returned to the View.

Action method for handling POST operation

This Action method handles the call made from the POST function from the View.

When the Form is submitted, the FruitId of selected Fruits are captured in the FrutIds parameter.

Then, a loop is executed over the FrutIds and the selected Fruit is fetched using Lambda expression.

Finally, the selected Fruit names are set into a ViewBag object which will be later displayed in View using JavaScript Alert Message Box.

Note: For more details on displaying message using JavaScript Alert MessageBox, please refer my article ASP.Net MVC Core: Display Message from Controller in View using JavaScript Alert MessageBox.

public class HomeController : Controller

{

private DBCtx Context { get; }

public HomeController(DBCtx _context)

{

this.Context = _context;

}

public IActionResult Index()

{

return View(this.PopulateFruits());

}

[HttpPost]

public IActionResult Index(string[]fruitIds)

{

List<SelectListItem> fruits = this.PopulateFruits();

if (fruitIds != null)

{

ViewBag.Message = "Selected Fruits:";

foreach (string fruitId in fruitIds)

{

SelectListItem selectedFruit = fruits.Find(p => p.Value == fruitId);

selectedFruit.Selected = true;

ViewBag.Message += "\\n" + selectedFruit.Text;

}

return View(fruits);

}

private List<SelectListItem> PopulateFruits()

{

List<SelectListItem>fruitsList = (from p in this.Context.Fruits

select new SelectListItem

{

Text = p.FruitName,

Value = p.FruitId.ToString()

}).ToList();

return fruitsList;

}

View

HTML Markup

Inside the View, in the very first line ASP.Net TagHelpers is inherited and Generic list of SelectListItem class is declared as Model for the View.

The View consists of an HTML Form with following ASP.Net Tag Helpers attributes.

asp-action – Name of the Action. In this case the name is Index.

asp-controller – Name of the Controller. In this case the name is Home.

method – It specifies the Form Method i.e. GET or POST. In this case it will be set to POST.

The HTML Form consists of a HTML Select (DropDownList), and a Submit Button.

The Model data has been assigned to the HTML Select (DropDownList) element using the asp-items Tag Helpers attribute.

The multiple attribute of the HTML Select (DropDownList) element is set which enables multiple selections.

Bootstrap Multiselect jQuery Plugin implementation

First, the jQuery and the JS and CSS files of the Bootstrap plugin and the jQuery Bootstrap Multi-Select plugin are inherited.

Inside the jQuery document ready event handler, the jQuery Bootstrap Multi-Select plugin is applied to the HTML Select (DropDownList) element.

Form Submission

When the Submit Button is clicked, the Form gets submitted and the values of the selected Fruits are sent to the Controller.

Finally, the multiple selected Fruit names are displayed using JavaScript Alert Message Box.

@addTagHelper*, Microsoft.AspNetCore.Mvc.TagHelpers

@model List<SelectListItem>

Layout = null;

}

<!DOCTYPE html>

<html>

<head>

<title>Index</title>

</head>

<body>

<form method="post" asp-controller="Home" asp-action="Index">

Fruits:

<select name="FruitIds" asp-items="Model" multiple="multiple" class="listbox"></select>

</form>

$(function () {

$('.listbox').multiselect({

includeSelectAllOption: true

});

</script>

@if (ViewBag.Message != null)

{

window.onload = function () {

alert("@ViewBag.Message");

};

</script>

}

</body>

</html>

Screenshot

Downloads

Download Code

ASP.Net Core MVC: Multiple Select (Multi-Select) DropDownList with CheckBoxes

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