controller not returning json result to view

Question

I am trying to update a checkbox list by using jquery to listen for a change. For some reason it seems that the controller method is not returning the JSON. I based this code on this example.

In the example the controller calls return Json(data, JsonRequestBehavior.AllowGet);, but I could only get return Json(data) working. My theory is that the return type has to specifically allow GET, but I dont know how to get that working.

My code works fine, with no errors and all 3 console statements appear in the web browser.

my jquery code (in my view):

$('#lgcheese').change(function() {
    ddToPopulate.empty();
    console.log('change detected');
    $.getJSON(CoIdUrl, { CoName: $(this).val() }, function (data) {
        console.log('in shit');
        if (!data) { console.log('no json returned');return;}
        ddToPopulate.append($('<ListItem></ListItem>').val('').text('Please select'));
        $.each(data, function(index, item) {
            ddToPopulate.append($('<ListItem></ListItem>').val(item.Value).text(item.Text));
        });
    });
});

later in my view I call: <CheckBoxList ID="cheesebox"></CheckBoxList> to create the checkbox list the jquery is supposed to populate.

My controller has method:

using System;
using System.Security.Claims;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
[HttpGet]
public JsonResult FetchCoIds(string CoName)
{
   var data = new { Value = "val", Text = CoName+"_val1" };
   return Json(data);
}

Answer 1

You need to update your action method with behavior. Try this

   [HttpGet]
    public JsonResult FetchCoIds(string CoName)
    {
        var data = new { Value = "val", Text = CoName+"_val1" };
        return Json(data, JsonRequestBehavior.AllowGet);
    }

Note:this answer is applicable for asp.net MVC not for Core