title: html.dropdownlistfor() troubles...getting null reference exceptions
body: <p>I've tried to follow a few examples from here and a couple other resources to just create a very simple member in my viewmodel and display it as a dropdown list on my view with a dropdownlistfor() helper.  I can't seem to wrap my head around it and it's not working with what I'm trying.</p>
  
  <p>here's my viewmodel:</p>
  
  <pre><code>public class Car
  {
      public int CarId { get; set; }
      public string Name { get; set; }
  }
  
  public class MyViewModel
  {
  
  
      public IEnumerable&lt;Car&gt; Cars = new List&lt;Car&gt; { 
          new Car {
              CarId = 1,
              Name = "Volvo"
          },
          new Car {
              CarId = 2,
              Name = "Subaru"
          }
      };
  
  
      public int MyCarId { get; set; }
  }
  </code></pre>
  
  <p>and here is my view:</p>
  
  <pre><code>@Html.DropDownListFor(m =&gt; m.MyCarId, new SelectList(Model.Cars, "CarId", "Name"))
  </code></pre>
  
  <p>and here is my controller:</p>
  
  <pre><code>public ActionResult MyView()
          {
              return View();
          }
  </code></pre>