No parameterless constructor defined for this object?

Question

I got above subjected error while POST the form and I think the root cause of subjected error is "DropDownListFor", where plural SelectList twice called, If Yes, please suggest the solution?

If I change from "x=>x.Values" to "x=>x.Name" then also get error "There is no ViewData item of type 'IEnumerable' that has the key 'DDLView.Name'."

Editor Template

@model DropDownListViewModel

@Html.LabelFor(x=>x.Values, Model.Label)
@Html.DropDownListFor(x=>x.Values, Model.Values)

View Model

public class HomePageViewModel
{
    public DropDownListViewModel DDLView { get; set; }
}

public class DropDownListViewModel
{
    public string Label { get; set; }
    public string Name { get; set; }
    public SelectList Values { get; set; }
}

Controller

public ActionResult Index()
    {
        HomePageViewModel homePageViewModel = new HomePageViewModel();

        homePageViewModel.DDLView = new DropDownListViewModel
                                        {
                                            Label = "drop label1",
                                            Name = "DropDown1",
                                            Values = new SelectList(
                                                         new[]
                                                             {
                                                                 new {Value = "1", Text = "text 1"},
                                                                 new {Value = "2", Text = "text 2"},
                                                                 new {Value = "3", Text = "text 3"},
                                                             }, "Value", "Text", "2"
                                                         )
                                        };
}

[HttpPost]
    public ActionResult Index(HomePageViewModel model)
    {
        return View(model);
    }

View

@model Dynamic.ViewModels.HomePageViewModel
@using (Html.BeginForm())
{
@Html.EditorFor(x=>x.DDLView)


<input type="submit" value="OK" />

}

Answer 1

The problem is that SelectList doesn't have parameterless constructor and model binder can't instantiate it, but you are trying to post it back.

To solve your problem change 2 things in your implementation:

1) Change in your editor template

 @Html.DropDownListFor(x=>x.Values, Model.Values) 

to

 @Html.DropDownListFor(x=>x.ValueId, Model.Values) 

2) add next to your original DropDownListViewModel

[ScaffoldColumn(false)]
public string ValueId { get; set; }

Now your post action parameter will be populated with correct values.