DropDownList not working 100% in ASP.Net MVC

Question

I am quite confused with how to effectively use the Html.DropDownList helper for ASP.NET MVC.

Background: I have a 5-page form, which saves data to the form each time "Next" is clicked. Users may navigate back and forth between sections, so previous sections will already be pre-populated with previously-entered data.

This works for TextBoxes. But not DropDownLists. I have tried a load of different methods, including:

• How to add static list of items in MVC Html.DropDownList()
• Setting selected item to DropdownList in MVC Application?

I have a ViewModel such taht I have got my lists and my Model (a LINQ-to-SQL generated class) as properties. eg:

public class ConsultantRegistrationFormViewModel
{
    public IConsultantRegistration ConsultantRegistration { get; private set; }

    public SelectList Titles { get; private set; }
    public SelectList Countries { get; private set; }
    public SelectList Currencies { get; private set; }
    public int CurrentSection { get; private set; }

    private ConsultantRegistrationFormViewModel(IConsultantRegistration consultantRegistration)
    {
        ConsultantRegistration = consultantRegistration;


        CurrentSection = 1;

        Titles = new SelectList(new string[] { "Mr", "Mrs", "Miss", "Ms", "Dr", "Sir" });
        Countries = new SelectList(countries.Select(q => q.Name));
        Currencies = new SelectList(currencies,"CurrencyCode","FriendlyForm");
    }
}

My Controller's Edit Action on GET looks like:

public class ConsultantRegistrationController : Controller
{
        public IConsultantRegistrationRepository ConsultantRegistrationRepository { get; private set; }
        public ICountryRepository CountryRepository { get; private set; }
    public IEnumerable<ICountry> Countries { get; private set; }

    public ConsultantRegistrationController()
    {
        ConsultantRegistrationRepository = RepositoryFactory.CreateConsultantRegistrationRepository();
        CountryRepository = RepositoryFactory.CreateCountryRepository();

        Countries = CountryRepository.GetCountries().ToArray();
    }


    public ActionResult Edit(Guid id, int sectionIndex)
    {
        IConsultantRegistration consultantRegistration = ConsultantRegistrationRepository.GetConsultantRegistration(id);

        SelectList bankBranchCountriesSelectList = new SelectList(Countries, "BankBranchCountry", "CountryName", consultantRegistration.BankBranchCountry);
        ViewData["bankBranchCountrySelectList"] = bankBranchCountriesSelectList;

        return View(new ConsultantRegistrationFormViewModel(consultantRegistration,sectionIndex,  Countries,Currencies));
    }
}

With my View doing:

        <%: Html.DropDownList("ConsultantRegistration.BankBranchCountry",ViewData["bankBranchCountrySelectList"] as SelectList) %>

This gives me the error:

DataBinding: 'IWW.ArrowPay.ConsultantRegistration.Data.Country' does not contain a property with the name 'BankBranchCountry'.

Which it does, have a look at the schema of this property:

public interface IConsultantRegistration
{
    Guid ID { get; set; }


    [DisplayName("Branch Country")]
    string BankBranchCountry { get; set; }

}

(My LINQ-to-SQL type ConsultantRegistration implemented IConsultantRegistration)

It seems that it is trying to bind to the wrong type, though?

If I use this in my view (and use my Controller's Countries property):

        <%: Html.DropDownList("ConsultantRegistration.BankBranchCountry ",Model.Countries,"(select a Country)") %>

I get the saved value fine, but my model doesn't update on POST.

And if I use this in my view:

        <%: Html.DropDownListFor(model=>model.ConsultantRegistration.BankBranchCountry ",Model.Countries,"(select a Country)") %>

I get the list, and it POSTs the selected value back, but does not pre-select the currently selected item in my model on the view.

So I have a bit of the solution all over the place, but not all in one place.

Hope you can help fill in my ignorance.

Answer 1

Ok, I solved it. Proper hacky, but it gets the job done.

I'm using the ViewData in my view:

                <%: Html.DropDownList("bankBranchCountrySelectList", ViewData["bankBranchCountrySelectList"] as SelectList)%>

With the following in my controller:

        public ActionResult Edit(Guid id, int sectionIndex)
        {
            IConsultantRegistration consultantRegistration = ConsultantRegistrationRepository.GetConsultantRegistration(id);

            ViewData["bankBranchCountrySelectList"] = Countries.Select(q => new SelectListItem() { Text = q.Name, Value = q.Name, Selected = (q.Name.Trim().Equals(consultantRegistration.BankBranchCountry, StringComparison.InvariantCultureIgnoreCase)) }); // bankBranchCountriesSelectList;

            return View(new ConsultantRegistrationFormViewModel(consultantRegistration,sectionIndex,  Countries,Currencies));
        }



        [AcceptVerbs(HttpVerbs.Post)]
        public ActionResult Edit(Guid id, int sectionIndex, FormCollection formValues)
        {
            IConsultantRegistration consultantRegistration = ConsultantRegistrationRepository.GetConsultantRegistration(id); 

            UpdateModel(consultantRegistration);
                    ViewData["bankBranchCountrySelectList"] = Countries.Select(q => new SelectListItem() { Text = q.Name, Value = q.Name, Selected = (q.Name.Trim().Equals(consultantRegistration.BankBranchCountry, StringComparison.InvariantCultureIgnoreCase)) });

            IEnumerable<RuleViolation> ruleViolations = consultantRegistration.GetRuleViolations(sectionIndex);
            if (ruleViolations.Count() == 0)
            {

// ...
            }
            else
            {
                ModelState.AddRuleViolations(ruleViolations);
                return View(new ConsultantRegistrationFormViewModel(consultantRegistration, sectionIndex, Countries, Currencies));
            }


    }

Not ideal and breaks clean coding. No idea why it works, but that seems to be what MVC is all about with "convention over configuration".

Answer 2

This article was written with Multi-Select Lists in mind, but the principle applies equally to a single-selection drop down list:

http://www.stevefenton.co.uk/Content/Blog/Date/201002/Blog/How-To-Handle-Multiple-Select-Lists-In-ASP-NET-MVC/