validate a dropdownlist in asp net mvc

Question

in controller ViewBag Categories   categoryRepository GetAllCategories   ToList       in view   Html DropDownList  Cat   new SelectList ViewBag Categories  ID    CategoryName      How can I make it so that by default it says  -Select Category-   And validate to check something is selected  client and on the model   Thanks

User · Answer

Example from MVC 4 for dropdownlist validation on Submit using Dataannotation and ViewBag (less line of code)

Models:

namespace Project.Models
{
    public class EmployeeReferral : Person
    {

        public int EmployeeReferralId { get; set; }


        //Company District
        //List                
        [Required(ErrorMessage = "Required.")]
        [Display(Name = "Employee District:")]
        public int? DistrictId { get; set; }

    public virtual District District { get; set; }       
}


namespace Project.Models
{
    public class District
    {
        public int? DistrictId { get; set; }

        [Display(Name = "Employee District:")]
        public string DistrictName { get; set; }
    }
}

EmployeeReferral Controller:

namespace Project.Controllers
{
    public class EmployeeReferralController : Controller
    {
        private ProjDbContext db = new ProjDbContext();

        //
        // GET: /EmployeeReferral/

        public ActionResult Index()
        {
            return View();
        }

 public ActionResult Create()
        {
            ViewBag.Districts = db.Districts;            
            return View();
        }

View:

<td>
                    <div class="editor-label">
                        @Html.LabelFor(model => model.DistrictId, "District")
                    </div>
                </td>
                <td>
                    <div class="editor-field">
                        @*@Html.DropDownList("DistrictId", "----Select ---")*@
                        @Html.DropDownListFor(model => model.DistrictId, new SelectList(ViewBag.Districts, "DistrictId", "DistrictName"), "--- Select ---")
                        @Html.ValidationMessageFor(model => model.DistrictId)                                                
                    </div>
                </td>

Why can't we use ViewBag for populating dropdownlists that can be validated with Annotations. It is less lines of code.

User · Answer

There is an overload with 3 arguments  Html DropdownList name  selectList  optionLabel  Update  there was a typo in the below code snippet    Html DropDownList  Cat   new SelectList ViewBag Categories  ID    CategoryName     -Select Category-     For the validator use   Html ValidationMessage  Cat

User · Answer

I just can t believe that there are people still using ViewData ViewBag in ASP NET MVC 3 instead of having strongly typed views and view models   public class MyViewModel        Required      public string CategoryId   get  set         public IEnumerable lt Category gt  Categories   get  set        and in your controller   public class HomeController  Controller       public ActionResult Index                 var model   new MyViewModel                       Categories   Repository GetCategories                     return View model               HttpPost      public ActionResult Index MyViewModel model                if   ModelState IsValid                           there was a validation error   gt                 rebind categories and redisplay view             model Categories   Repository GetCategories                return View model                        At this stage the model is OK   gt  do something with the selected category         return RedirectToAction  Success              and then in your strongly typed view    Html DropDownListFor      x   gt  x CategoryId       new SelectList Model Categories   ID    CategoryName          -- Please select a category --     Html ValidationMessageFor x   gt  x CategoryId    Also if you want client side validation don t forget to reference the necessary scripts    lt script src   Url Content    Scripts jquery validate js    type  text javascript  gt  lt  script gt   lt script src   Url Content    Scripts jquery validate unobtrusive js    type  text javascript  gt  lt  script gt

User · Answer

For ListBox   DropDown in MVC5 - i ve found this to work for me sofar   in Model     Required ErrorMessage    - Select item -     public List lt string gt  SelectedItem   get  set     public List lt SelectListItem gt  AvailableItemsList   get  set      in View    Html ListBoxFor model   gt  model SelectedItem  Model AvailableItemsList   Html ValidationMessageFor model   gt  model SelectedItem      new    class    text-danger

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