Question

I have a partial view with a DropDownList control and a textbox.

When nothing is selected or no text is entered the ModelState.IsValid is FALSE

BUT I can see no validation errors displayed annotated on my properties.

Why is that? I can see in the ModelState.Value.Errors property there is an “Name is

missing” for example.

When I confirm the invalid view I see this in my output window:

A first chance exception of type 'System.InvalidOperationException' occurred in System.Web.Mvc.dll
A first chance exception of type 'System.InvalidOperationException' occurred in System.Web.Mvc.dll
A first chance exception of type 'System.InvalidOperationException' occurred in System.Web.Mvc.dll


public ActionResult Edit()
{
    return LoadEditTemplates();
}


[HttpPost]
public ActionResult Update(EditTemplateListViewModel viewModel)
{
    if (ModelState.IsValid && !_templateDataProvider.TemplateExists(viewModel.Name))
    {
        Template template = Mapper.Map<EditTemplateListViewModel, Template>(viewModel);
        _templateDataProvider.UpdateTemplate(template);
        return new JsonNetResult(new { success = true });
    }

    return PartialView(viewModel);
}

private ActionResult LoadEditTemplates()
{
    var templates = _templateDataProvider.GetTemplates();
    EditTemplateListViewModel editTemplateViewModel = new EditTemplateListViewModel()
    {
        DisplayList = Mapper.Map<IEnumerable<Template>, IEnumerable<TemplateViewModel>>(templates),
    };
    return PartialView(editTemplateViewModel);
}

public class EditTemplateListViewModel
    {
        [Required(ErrorMessage = "No template selected.")]
        public int TemplateId { get; set; }

        [Required(ErrorMessage="Name is missing")]
        public string Name { get; set; }

        public IEnumerable<TemplateViewModel> DisplayList { get; set; }      
    }

@model ITMS.Web.Models.EditTemplateListViewModel

@*Remote Validation*@
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>

@using (Html.BeginForm("Update", "Template"))
{       
    @Html.ValidationSummary(false)
    @Html.DropDownListFor(x => x.TemplateId, new SelectList(Model.DisplayList, "TemplateId", "Name"), new { @class = "listviewmodel" })

    <p class="editor-label">@Html.LabelFor(model => model.Name)</p>
    <p class="editor-field">@Html.EditorFor(model => model.Name)</p>
    <p class="editor-field">@Html.ValidationMessageFor(model => model.Name)</p>   
}

Answer 1

When I returned the data from the post action I realized the Argument cast exception because I did not pass data for example to the SelectItem list “DisplayList”. It was null and thus bang…

I just filled the missing data to redisplay the view and the errors are visible 🙂 heck… I already stepped in that failure once…