Question

May be I just don’t know how to google, but I am trying to find an example where a dropdown control is data-binded to a collection (this part is working for me) and then I want to read the drop down selection back into a variable. This variable could be a property on the mode. Binding dropdown selected value back into variable is where I am having troube. In web-forms world this was no big deal but for some reason I cannot make it work with MVC 3. Any code samples or examples will be highly appreciated.

Answer 1

The recommended way to do this in ASP.NET MVC is to use a view model. When you design a dropdownlist you need 2 properties on this view model: one that will be used to bind the selected value to and a second one which represents a collection of values and texts which will be used to generate the options. Then you could use the first property to preselect a given option.

So we start by designing view model:

public class MyViewModel
{
    public string SelectedId { get; set; }
    public IEnumerable<SelectListItem> Items { get; set; }
}

then a controller action which populate this view model:

public ActionResult Index()
{
    var model = new MyViewModel
    {
        // preselect the second item which has value=2
        SelectedId = "2",

        Items = new[]
        {
            new SelectListItem { Value = "1", Text = "item 1" },
            new SelectListItem { Value = "2", Text = "item 2" },
            new SelectListItem { Value = "3", Text = "item 3" },
        }
    };
    return View(model);
}

and in the strongly typed view use the DropDownListFor helper to generate the dropdown:

@model MyViewModel
@Html.DropDownListFor(
    x => x.SelectedId, 
    Model.Items,
    "-- Select an Item --"
)