Question

When I submit a form, my Courses List into my ViewModel is getting null values.
This is my ViewModel:

public class CandidateViewModel
{
    public string Name { get; set; }
    public IList<CourseViewModel> Courses { get; set; }

    public CandidateViewModel()
    {
        Name = "Kiwanax";
        Courses = new List<CourseViewModel>();
        for (int count = 0; count < 5; ++count)
        {
            Courses.Add(new CourseViewModel( 
                string.Format("Course_{0}", count), 5));
        }
    } 
}

public class CourseViewModel
{
    public long ID { get; set; }
    public string Name { get; set; }
    public OptionViewModel SelectedOption { get; set; }
    public IList<OptionViewModel> Options { get; set; }

    public CourseViewModel(string name, int numberOfOptions) 
    {
        Name = name;
        Options = new List<OptionViewModel>();
        for (int count = 1; count <= numberOfOptions; ++count)
        {
            Options.Add(new OptionViewModel(count.ToString(), 
                string.Format("Option {0}", count)));
        }
        SelectedOption = Options[0];
    }
}

public class OptionViewModel
{
    public string Value { get; set; }
    public string Description { get; set; }
}

OK. When I create DropDownLists based on my IList, it works fine.

<ul id="cursos">
@for (int count = 0; count < Model.Courses.Count; ++count)
{
    <li>
        @Html.DropDownListFor(i => i.Courses[count].SelectedOption,
            new SelectList(Model.Courses[count].Options, "Value", "Description", Model.Courses[count].SelectedOption))
                @Html.HiddenFor(i => i.Courses[count].ID)
                @Model.Courses[count].Name
            </li>
        }
        </ul>

But, when I do post from my form, I’m getting null values from that IList.

Answer 1

You cannot bind dropdowns to complex property values:

i => i.Courses[count].SelectedOption

It must be bound to the corresponding primitive type that will be sent to the server:

i => i.Courses[count].SelectedOption.Value

Remember that in HTML the <select> element only sends the selected value as a simple string type to the server.