asp.net mvc core select2 dropdown autopopulate ajax call

Question

I have a view where I am trying to implement the auto populate the text box/drop down field. I am using a list which I query on.

I am following this example http://www.dotnetqueries.com/Article/159/how-to-implement-select2-with-ajax-and-json-in-asp-net-mvc , break point does not even hit the method in my controller. so is there something wrong with the way I set this up or the way the action result method is called in controller.

using System.Collections.Generic;
using System.Linq;
using System.Web.Mvc;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using TestSelect2.Models;
using Controller = Microsoft.AspNetCore.Mvc.Controller;
    
    namespace TestSelect2.Controllers
    {
        public class HomeController : Controller
        {
            private readonly ILogger<HomeController> _logger;
    
            public HomeController(ILogger<HomeController> logger)
            {
                _logger = logger;
            }
    
            public IActionResult Index()
            {
                return View();
            }
    
          
            [Microsoft.AspNetCore.Mvc.HttpPost]
            [Microsoft.AspNetCore.Mvc.Route("/home/account-list")]
            public Microsoft.AspNetCore.Mvc.ActionResult GetAccounts(string q)
            {
                List<Account> accounts = new List<Account>();
                // Add parts to the list.
                accounts.Add(new Account() { Id = 1, AccountNumber = "MVP1" });
                accounts.Add(new Account() { Id = 1, AccountNumber = "MVP11" });
                accounts.Add(new Account() { Id = 1, AccountNumber = "ABC2" });
                accounts.Add(new Account() { Id = 1, AccountNumber = "ABC3" });
                accounts.Add(new Account() { Id = 1, AccountNumber = "XYZ3" });
                accounts.Add(new Account() { Id = 1, AccountNumber = "XYZ4" });
    
     
                        
                    if (!(string.IsNullOrEmpty(q) || string.IsNullOrWhiteSpace(q)))
                    {
                        accounts = accounts.Where(x => x.AccountNumber.ToLower().StartsWith(q.ToLower())).ToList();
                    }
                    return Json(new { items = accounts }, JsonRequestBehavior.AllowGet);
            }
          
    
        }
    }



    @{
        Layout = null;
    }
    <!DOCTYPE html>
    <html>
    <head>
        <meta name="viewport" content="width=device-width" />
        <title>Select2 DEMO</title>
        <link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.6-rc.0/css/select2.min.css" rel="stylesheet" />
        <script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.6-rc.0/js/select2.min.js"></script>
    
        <script>
            $(document).ready(function () {
                $(".accountSelect").select2({
                    ajax: {
                        url: '/home/account-list',
                        width: 'resolve',
                        data: function (params) {
                            return {
                                q: params.term// search term
                            };
                        },
                        processResults: function (data) {
                            return {
                                results: data.items
                            };
                        },
                        minimumInputLength: 2,
                        width: 'resolve'
                    }
                });
     
            });
        </script>
        <style>
            body {
                margin: auto;
                width: 600px;
                padding: 50px;
            }
    
            .accountSelect {
                width: 400px;
            }
        </style>
    </head>
    <body>
    <form method="post">
    
        <select class="accountSelect"></select>
    </form>
    </body>
    </html>

mj1313 · Accepted Answer · 2020-08-06 05:44:13Z

Remove the [HttpPost] attribute on GetAccounts action. Since the ajax makes a get request.And the tutorial you follow is for asp.net but not asp.net core, there is no JsonRequestBehavior.

Note: select2model must with id and text two properties, otherwise, it can't be recognized. Change your Account model like below:

public class Account
{
    public int Id { get; set; }
    public string Text { get; set; }
}

And the controller action, make sure the id can't be the same.

[Route("/home/account-list")]
public IActionResult GetAccounts(string q)
{
    List<Account> accounts = new List<Account>();
    // Add parts to the list.
    accounts.Add(new Account() { Id = 1, Text = "MVP1" });
    accounts.Add(new Account() { Id = 2, Text = "MVP11" });
    accounts.Add(new Account() { Id = 3, Text = "ABC2" });
    accounts.Add(new Account() { Id = 4, Text = "ABC3" });
    accounts.Add(new Account() { Id = 5, Text = "XYZ3" });
    accounts.Add(new Account() { Id = 6, Text = "XYZ4" });


    if (!(string.IsNullOrEmpty(q) || string.IsNullOrWhiteSpace(q)))
    {
        accounts = accounts.Where(x => x.Text.ToLower().StartsWith(q.ToLower())).ToList();
    }
    return Json(new { items = accounts });
}

View and Scripts:

@{
    Layout = null;
}
<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Select2 DEMO</title>
    <link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.6-rc.0/css/select2.min.css" rel="stylesheet" />
    <script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.6-rc.0/js/select2.min.js"></script>

    <script>
        $(document).ready(function () {
            $(".accountSelect").select2({
                minimumInputLength: 2,
                ajax: {
                    url: '/home/account-list',
                    data: function (params) {
                        return {
                            q: params.term// search term
                        };
                    },
                    processResults: function (data) {
                        return {
                            results: data.items
                        }
                    },
                }
            });
        });
    </script>

    <style>
        body {
            margin: auto;
            width: 600px;
            padding: 50px;
        }

        .accountSelect {
            width: 400px;
        }
    </style>
</head>
<body>
    <form method="post">
        <select class="accountSelect"></select>
    </form>

</body>
</html>

Result:

Ashish Tripathi · Accepted Answer · 2020-08-06 05:21:05Z

You may try as below:

//1. Action Method Which Returns the data. 
public ActionResult GetSelect2Data(string query)
{
    //In Realtime This should come from the Database
    List<DropDownItem> collection = new List<DropDownItem>() {
        new DropDownItem(){ Value = 1,  Text = "Switzerland"},
        new DropDownItem(){ Value = 2,  Text = "Canada"},
        new DropDownItem(){ Value = 3,  Text = "Japan"},
        new DropDownItem(){ Value = 4,  Text = "Germany"},
        new DropDownItem(){ Value = 5,  Text = "Australia"},
        new DropDownItem(){ Value = 6,  Text = "United Kingdom"},
        new DropDownItem(){ Value = 7,  Text = "United States"},
        new DropDownItem(){ Value = 8,  Text = "Sweden"},
        new DropDownItem(){ Value = 9,  Text = "India"},
       new DropDownItem(){ Value = 10,  Text = "Russia"},
     };


        var searchResult = from c in collection
                           where c.Text.Contains(query, 
   StringComparison.CurrentCultureIgnoreCase)
                           select c;

        return Json(searchResult.ToList());
    }



///2. JS Method which binds any HTML Select as Select2 or Smart Select.   
///In the User Interface (.cshtml file)You may define a framework JS Function as  which could be used anywhere
function registerSelect2(dropDownSelector, ajaxUrl) {
$(dropDownSelector).select2({
    ajax: {
    url: ajaxUrl,
    dataType: 'json',
    delay: 10,
    type: 'GET',
    data: function (params) {
    return {
        query: params.term, // search term
    };
    }
    , processResults: function (data) {
    return {
    results: $.map(data, function (item) {
        return {
            id: item.value,
            text: item.text,
        };
    })
    };
    },
    cache: true,
},
    minimumInputLength: 3,
    allowHtml: true,
    allowClear: true
});
}


//3. Invoke the JS Function to make any particular Select a Select2. 
$(function () {
    //Just you need to pass the Selector of your control and the Ajax Url from which data has to be loaded
    registerSelect2("#ddlSelect2", "/user/GetSelect2Data");
});


//This is the Simple Select which's made a Select2 Control. Paste it somewhere in the UI
<select id="ddlSelect2"></select>

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