DropDownList not working 100% in ASP.Net MVC - 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/