An unhandled exception occurred while processing the request. ArgumentNullException: Value cannot be null. Parameter name: items Microsoft.AspNetCore.Mvc.Rendering.MultiSelectList..ctor(IEnumerable items, string dataValueField, string dataTextField, IEnum

Question

public void candidatename()
        {
            List<SelectListItem> name = new List<SelectListItem>();
            string apiUrl = "http://localhost:54621/api/mim/candidate/GetCandidates";
            Util du = new Util();
            string respText = "";
            string isErr = "";
            respText = du.CallingAPI(out isErr, apiUrl);
            respText = respText.TrimStart('\"');
            respText = respText.TrimEnd('\"');
            respText = respText.Replace("\\", "");


            List<SelectListItem> candidatelist = new List<SelectListItem>();

            Interviewer obj = new Interviewer();

            List<Interviewer> objLst = new List<Interviewer>();

            if (isErr != "Err" && isErr != "err")
            {
                List<JObject> ob = JsonConvert.DeserializeObject<List<JObject>>(respText);

                foreach (JObject job in ob)
                {
                    SelectListItem s = new SelectListItem
                    {
                        Value = job.Property("Id").Value.ToString(),
                        Text = job.Property("Candidatename").Value.ToString()
                    };
                    candidatelist.Add(s);
                    
                }
            }
            candidatelist.Insert(0, new SelectListItem { Text = "--Select--", Value = "0" });

            ViewBag.candidatelist = candidatelist;
        }
[HttpPost]
        public ActionResult Form(Candidate s)
        {

            HttpClient client = new HttpClient();
            client.BaseAddress = new Uri("http://localhost:54621/api/mim/candidate/SaveC");
            client.DefaultRequestHeaders.Accept.Clear();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
            HttpResponseMessage response = client.PostAsJsonAsync("http://localhost:54621/api/mim/candidate/SaveC", s).Result;
            string result = response.Content.ToString();
            return View();
        }



@model Form3.Models.Interviewer

@{
    ViewData["Title"] = "Form";
}

<h2>Form</h2>

<h4>Interviewer</h4>
<hr />
<div class="row">
    <div class="col-md-4">
        <div class="form-group">
            <label asp-for="Candidatename" class="control-label"></label>
            <select asp-items="@(new SelectList(@ViewBag.candidatelist, "Value", "Text", @ViewBag.candidatelistSelected))" class="form-control" id="ddlApplication" onchange="ShowAPI('')"></select>
       


   
        </div>
        <form asp-action="Form">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>


            <div class="form-group">
                <label asp-for="Candidatename" class="control-label"></label>
                <div>
                    <label>@ViewBag.d</label>
                </div>
            </div>

            <div class="form-group">
                <label asp-for="Dateofinterview" class="control-label"></label>
                <div>
                    <lebel>@ViewBag.a</lebel>
                </div>
                <div>
                    <label asp-for="Timeofinterview" class="control-label"></label>
                    <div>
                        <lebel>@ViewBag.b</lebel>
                    </div>
                </div>
                <label asp-for="Postappliedfor" class="control-label"></label>
                <div>
                    <label>@ViewBag.c</label>
                </div>
                @*<select asp-items="@(new SelectList(@ViewBag.candidatedatelist, "Value", "Text", @ViewBag.candidatedatelistSelected))"  onchange="FillModel();" class="form-control" ></select>*@
            </div>
            @*<div class="form-group">
            <label asp-for="Timeofinterview" class="control-label"></label>
            <select asp-items="@(new SelectList(@ViewBag.candidatetimelist, "Value", "Text", @ViewBag.candidatetimelistSelected))" onchange="FillModel();" class="form-control"></select>
            </div>
            <div class="form-group">
            <label asp-for="Postappliedfor" class="control-label"></label>
            <select asp-items="@(new SelectList(@ViewBag.candidatepostlist, "Value", "Text", @ViewBag.candidatepostlistSelected))" onchange="FillModel();" class="form-control"></select>
            </div>

            <div class="form-group">
            <label asp-for="Overallhrrating" class="control-label"></label>
            <select asp-items="@(new SelectList(@ViewBag.candidateratinglist, "Value", "Text", @ViewBag.candidateratinglistSelected))" onchange="FillModel();" class="form-control"></select>
            </div>*@

            <div class="form-group">
                <label asp-for="technicalskills" class="control-label"></label>
                <div>
                    <input type="radio" id="1" name="technicalskills" value="1" class="form-check-input">
                    <label for="1" style="color:orange">★</label><br>
                    <input type="radio" id="2" name="technicalskills" value="2" class="form-check-input">
                    <label for="2" style="color:orange">★★</label><br>
                    <input type="radio" id="3" name="technicalskills" value="3" class="form-check-input">
                    <label for="3" style="color:orange">★★★</label><br>
                    <input type="radio" id="4" name="technicalskills" value="4" class="form-check-input">
                    <label for="4" style="color:orange">★★★★</label><br>
                    <input type="radio" id="5" name="technicalskills" value="5" class="form-check-input">
                    <label for="5" style="color:orange">★★★★★</label><br>
                </div>
                <span asp-validation-for="technicalskills" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="interviewerremarks" class="control-label"></label>
                <div>
                    <input type="radio" id="1" name="interviewerremarks" value="1" class="form-check-input">
                    <label for="1" style="color:yellow">★</label>
                    &nbsp;&nbsp;&nbsp;&nbsp;
                    <input type="radio" id="2" name="interviewerremarks" value="2" class="form-check-input">
                    <label for="2" style="color:yellow">★★</label>
                    &nbsp;&nbsp;&nbsp;&nbsp;
                    <input type="radio" id="3" name="interviewerremarks" value="3" class="form-check-input">
                    <label for="3" style="color:yellow">★★★</label>
                    &nbsp;&nbsp;&nbsp;&nbsp;
                    <input type="radio" id="4" name="interviewerremarks" value="4" class="form-check-input">
                    <label for="4" style="color:yellow">★★★★</label>
                    &nbsp;&nbsp;&nbsp;&nbsp;
                    <input type="radio" id="5" name="interviewerremarks" value="5" class="form-check-input">
                    <label for="5" style="color:yellow">★★★★</label>
                </div>
                <span asp-validation-for="interviewerremarks" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="statusfornextround" class="control-label"></label>
                <div>
                    <input type="checkbox" id="SELECTED" name="statusfornextround" value="SELECTED" onclick="onlyOne(this)" class="form-check-input">
                    <label for="SELECTED"> SELECTED</label>
                    &nbsp;
                    &nbsp;&nbsp;&nbsp;
                    <input type="checkbox" id="REJECTED" name="statusfornextround" value="REJECTED" onclick="onlyOne(this)" class="form-check-input">
                    <label for="REJECTED"> REJECTED</label>
                    &nbsp;
                    &nbsp;&nbsp;&nbsp;
                    <input type="checkbox" id="NOSHOW" name="statusfornextround" value="NOSHOW" onclick="onlyOne(this)" class="form-check-input">
                    <label for="NOTSHOW">NO SHOW</label>
                </div>

                <span asp-validation-for="statusfornextround" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Remark" class="control-label"></label>
                <textarea id="HRremarks" name="HRremarks" rows="4" cols="50" class="text-danger">
                    @*<input asp-for="Remark" class="form-control" />*@
Feedback.
</textarea>
                <span asp-validation-for="Remark" class="text-danger"></span>
            </div>
            <div class="form-group">
                <input type="submit" value="Create" class="btn btn-default" onchange="alert('Selected');" />
            </div>
        </form>
    </div>

</div>
<script>
    function onlyOne(checkbox) {
        var checkboxes = document.getElementsByName('statusfornextround')
        checkboxes.forEach((item) => {
            if (item !== checkbox) item.checked = false
        })
    }

    function ShowAPI(SubApp) {
        var AppID = $('#ddlApplication').val();
        //var ddlSubApp = $('#ddlSubApp');
        alert(AppID);
        $.ajax({
            url: "../Candidate/Getcandidatedetail",
            data: "{ 'Id': '" + AppID + "'}",
            type: "Post",
            contentType: "application/json;charset=utf-8",
            success: function (data) {
                //alert(AppID)

            },
            failure: function (data) {
                alert(data.statusText);
            },
            error: function (error) {
                alert(error.statusText);
            }
        });
    }
</script>
<div>
    <a asp-action="Index">Back to List</a>
</div>



At the time of saving showing error


An unhandled exception occurred while processing the request.
ArgumentNullException: Value cannot be null.
Parameter name: items
Microsoft.AspNetCore.Mvc.Rendering.MultiSelectList..ctor(IEnumerable items, string dataValueField, string dataTextField, IEnumerable selectedValues, string dataGroupField)

Stack Query Cookies Headers
ArgumentNullException: Value cannot be null. Parameter name: items
Microsoft.AspNetCore.Mvc.Rendering.MultiSelectList..ctor(IEnumerable items, string dataValueField, string dataTextField, IEnumerable selectedValues, string dataGroupField)
Microsoft.AspNetCore.Mvc.Rendering.SelectList..ctor(IEnumerable items, string dataValueField, string dataTextField, object selectedValue)
CallSite.Target(Closure , CallSite , Type , object , string , string , object )
AspNetCore.Views_Candidate_Form.ExecuteAsync() in Form.cshtml
+
            <select asp-items="@(new SelectList(@ViewBag.candidatelist, "Value", "Text", @ViewBag.candidatelistSelected))" class="form-control" id="ddlApplication" onchange="ShowAPI('')"></select>
Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageCoreAsync(IRazorPage page, ViewContext context)
Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageAsync(IRazorPage page, ViewContext context, bool invokeViewStarts)
Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderAsync(ViewContext context)
Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, string contentType, Nullable<int> statusCode)
Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ActionContext actionContext, IView view, ViewDataDictionary viewData, ITempDataDictionary tempData, string contentType, Nullable<int> statusCode)
Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor.ExecuteAsync(ActionContext context, ViewResult result)
Microsoft.AspNetCore.Mvc.ViewResult.ExecuteResultAsync(ActionContext context)
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeResultAsync(IActionResult result)
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResultFilterAsync<TFilter, TFilterAsync>()
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResultExecutedContext context)
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.ResultNext<TFilter, TFilterAsync>(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeResultFilters()
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResourceFilter()
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context)
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeFilterPipelineAsync()
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeAsync()
Microsoft.AspNetCore.Builder.RouterMiddleware.Invoke(HttpContext httpContext)
Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

Answer 1

The Form action does not populate the @ViewBag.candidatelist.