title: Value cannot be null. Parameter name: source in MVC listbox
body: <p>I have found plenty of posts about this, but none of them are solving my issue.  My code right now:</p>
  
  <pre><code>@Html.ListBox("SelectedNewsletter", Model.Newsletters)
  </code></pre>
  
  <p>and</p>
  
  <pre><code>public MultiSelectList Newsletters
  {
      get
      {
  
              return new MultiSelectList(
              new[] 
              {
                  // TODO: Fetch from your repository
                  new { Id = 1, Name = "item 1" },
                  new { Id = 2, Name = "item 2" },
                  new { Id = 3, Name = "item 3" },
              },
              "Id",
              "Name"
                  );
  
        //      return new MultiSelectList(PromoNewsletter.All, "IdString", "Display");
      }
  }
  </code></pre>
  
  <p>As far as I can see, it's all hard coded now, and it still gives the same error.  I want to do a ListboxFor, but I am trying to just get a listbox to work.  I have replaced my int id with a string representation, based on advice I found elsewhere, but now I don't see what else I can do.  It just plain is not working, even with all hard coded values and not binding to a property on my ViewModel.  Where am I going wrong ?</p>