I try to create dropdown list. But it give me error. First dropdown is working which I try with simple list. But in second dropdown which I create with Value and text It give me error.

I adopted code first approach and created bool type property in model class. I want Yes or No form user through dropdown list and store its corresponding value in database for yes value is 1 and for No value is 0. So I try SelectListItem to pass the value and text to View. But its not working:

Here is my model class:

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

namespace Edu_Form.Models
{
    public class Hiring_Edu_Info
    {
        [Key]
        public int Id { get; set; }
        public String Level { get; set; }
        public bool IsDegreeCompleted { get; set; }
    }
} 

Here is my controller:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace Edu_Form.Controllers
{
    public class HiringController : Controller
    {
        // GET: Hiring
        public ActionResult Index()
        {
            List<SelectListItem> DegreeCompleted = new List<SelectListItem>() {
                      new SelectListItem {
                          Text = "Yes", Value = "1"
                      },
                      new SelectListItem {
                          Text = "No", Value = "0"
                      },
                };

            ViewBag.LevelList = DegreeCompleted;
            return View();
        }
}

Here is my view:

@model Edu_Form.Models.VMHiring_edu_Info

@{
    ViewBag.Title = "Index";
}

<h2>Index</h2>


@using (Html.BeginForm())
{
    @Html.AntiForgeryToken()
<div >
                    @Html.LabelFor(model => model.IsDegreeCompleted, htmlAttributes: new { @class = "control-label " })
                    <div >

                        @Html.DropDownListFor(model => model.IsDegreeCompleted, new SelectList(ViewBag.DegreeCompleted, "Value", "Text"), "-- Select --", new { @class = "form-control" })
                        @* @Html.EditorFor(model => model.IsDegreeCompleted)*@
                        @Html.ValidationMessageFor(model => model.IsDegreeCompleted, "", new { @class = "text-danger" })

                    </div>
                </div>

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

This line throws an error:

@Html.DropDownListFor(model => model.IsDegreeCompleted, new SelectList(ViewBag.DegreeCompleted, "Value", "Text"), "-- Select --", new { @class = "form-control" })

Error details:

System.ArgumentNullException
HResult=0x80004003
Message=Value cannot be null.
Parameter name: items
Source=System.Web.Mvc

StackTrace:

at System.Web.Mvc.MultiSelectList..ctor(IEnumerable items, String dataValueField, String dataTextField, String dataGroupField, IEnumerable selectedValues, IEnumerable disabledValues, IEnumerable disabledGroups)
at ASP._Page_Views_NUML_Hiring_Index_cshtml.Execute() in C:\Users\Shaheer_Ahmed\Desktop\HRM_NUML\Edu_Form\Edu_Form\Views\NUML_Hiring\Index.cshtml:line 71
at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
at System.Web.WebPages.StartPage.RunPage()
at System.Web.WebPages.StartPage.ExecutePageHierarchy()
at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance)
at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer)
at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)

CodePudding user response：

Build the SelectList under your controller and pass to the view through viewbag

 var OType = new List<SelectListItem>();
                OType.Add(new SelectListItem() { Text = "Yes", Value = "0" });
                OType.Add(new SelectListItem() { Text = "No", Value = "1" });
    
                SelectList DegreeCompleted = new SelectList(OType, "Value", "Text");
    
    ViewBag.DegreeCompleted = DegreeCompleted ;

Under the view, you can do something like this.

@Html.DropDownListFor(model => model.IsDegreeCompleted, (SelectList)ViewBag.DegreeCompleted, "-- Select --", new { @class = "form-control" })

If you want to add value to the DropDownList, you can do like

 @Html.DropDownListFor(model => model.IsDegreeCompleted, (SelectList)ViewBag.DegreeCompleted, "-- Select --", new { @class = "form-control", @Value = @item.value })