DropdownListFor - Null Reference Exception on page model

I'm trying to save one of my Models to the database. Given the models:

public class Foo {
     public int Id { get; set; }
     public string Name { get; set; }
     public virtual Bar Something { get; set; }
}

public class Bar {
     public int Id { get; set; }
     public string Name { get; set; }
}

public class FooPageModel {
    public Foo F { get; set; }
    public List<SelectListItem> Bars { get; set; }
}

In my controller I have:

public ActionResult Add(){
     var bars = ... // get all bars from db context
     var barsList = new List<SelectListItem>();
     barsList.AddRange(bars.Select(b => new SelectListItem {
          Text = b.Name,
          Value = b.Name
     }));

     var model = new FooPageModel
     {
          Bars = barsList
     };
     return View("Add", model);
 }

Now for the View (strongly typed to FooPageModel):

<%: Html.DropdownListFor(f => f.F.Bar, Model.Bars) %>

The view renders fine, with the values I 开发者_如何学Cexpect, but when I submit the page form, I get a NullReferenceException (on the view line pasted above before the action on the controller is ever reached). I thought maybe if I modified my controller code to:

var model = new FooPageModel
{
     F = new Foo(),
     Bars = barsList
}

However, this fails as well. I suppose I could re-write FooPageModel to just be a list of strings of the information I want, but it seems redundant to duplicate Model logic; I'm pretty new to CTP in general, so maybe that's how it's done?

I was able to code up something similar for a ComplexType (an address Model) and had no problems. If the stack trace would be helpful, let me know and I'll post it. Thanks in advance.

---

You aren't showing the code where you return the ActionResult, but you need to make sure you are passing the model to the view, like this:

public ActionResult Add() {
    ...

    return View(model);  // send the model to the view
}