Validating required selection in DropDownList

Question

My view model defines property which has to be displayed as combo box. Property definition is:

[Required]
public int Processor { get; set; }

<

Answer 1

How about this:

[Required]
public int? Processor { get; set; }

And then:

<%= Html.DropDownListFor(
    x => x.Processor, Model.Processors, "-- select processor --"
) %>

And in your POST action

[HttpPost]
public ActionResult Index(MyViewModel model)
{
    if (ModelState.IsValid)
    {
        // the model is valid => you can safely use model.Processor.Value here:
        int processor = model.Processor.Value;
        // TODO: do something with this value
    }
    ...
}

And now you no longer need to manually add the noSelection item. Just use the proper DropDownListFor overload.