Cadecading dropdown list not working , , when I publish in IIS , but in visual studio 2015 working fine , by using ASP.NET MVC code first

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C#

i create the script call function in mvc controller , it's working good in visual studio, but when i converted to IIS website , all website working good else casecading dropdownlist ,,,

my code (

=========================================================

function

public ActionResult FillDept(string level)
  {

         var depart = db.Departments.Where(c => c.LevelId == level);
             return Json(depart, JsonRequestBehavior.AllowGet);

  }

script in html view

<script>

    function FillDept() {
        var levelId = $('#Level').val();
        $.ajax({
            url: '/Trainees/FillDept',
            type: "GET",
            dataType: "JSON",
            data: { Level: levelId },
            success: function (depart) {
                $("#Department").html(""); // clear before appending new list
                $.each(depart, function (i, department) {
                    $("#Department").append(
                        $('<option></option>').val(department.DeptId).html(department.DeptName))


                });
            }
        });
    }
</script>

dropdwonlist

 @Html.LabelFor(m => m.Level, new { @class = "control-label col-md-1" })
 <div class="col-md-3 jumbotron">
     @Html.DropDownListFor(m => m.Level,
        new SelectList(ViewBag.LevelList, "LevelId", "LevelName"),
        "level",
       new { @class = "form-control", @onchange = "FillDept()" })
     @Html.ValidationMessageFor(m => m.Level, "", new { @class = "text-danger" })

 </div>



 @Html.LabelFor(m => m.Department, new { @class = "control-label col-md-1" })
 <div class="col-md-3 jumbotron">
     @Html.DropDownListFor(m => m.Department,
new SelectList(Enumerable.Empty<SelectListItem>(), "DeptId", "DeptName"),
       "department", new { @class = "form-control" })
     @Html.ValidationMessageFor(m => m.Department, "", new { @class = "text-danger" })

 </div>

)

What I have tried:

Hi there , i need to help please ..

asp.net MVC code first