ASP.NET MVC Populating dropdownlist - asp.net-mvc-4

Question

I've been trying to populate a dropdownlist for a while now and would appreciate some help. I have my model and viewmodel and my trying to populate the Dropdownlist and send it to the view so a user can choose a cartype and click submit.
public class Cars
{
public int CarId { get; set; }
public string Name { get; set; }
}
public class CarViewModel
{
public int SelectedCarId { get; set; }
public IEnumerable<SelectListItem> CarTypes;
}
public ActionResult FillDropDown()
{
var model = new ViewModel();
model.CarTypes = (from s in context.CarTypes
select new SelectListItem()
{
Text = s.Name,
Value = SqlFunctions.StringConvert((double)s.Id).Trim(),
}).ToList<SelectListItem>();
return View(model);
}
So I would like some help how to render this in the view. I tried the following but I get a nullreference exception.
#Html.BeginForm("FillDropDownList","Home", FormMethod.Post,null)
{
#Html.DropDownListFor(x => x.SelectedCarId, Model.CarTypes);
<input type="submit" value="submit" />
}

Answer 1

Try to use CarViewModel instead of ViewModel.
public ActionResult FillDropDown()
{
var model = new CarViewModel(); //CarViewModel instead of ViewModel
model.CarTypes = (from s in context.CarTypes
select new SelectListItem()
{
Text = s.Name,
Value = SqlFunctions.StringConvert((double)s.Id).Trim(),
}).ToList<SelectListItem>();
return View(model);
}
EDIT:
Change your IEnumerable property in CarViewModel into SelectList
public class CarViewModel
{
public int SelectedCarId { get; set; }
public SelectList CarTypes;
}
Make sure the SelectListItem is not null, in the FillDropDown() method.