null reference binding jqgrid to object that contains sub objects - jqgrid

Question

Does anyone know why the following c# mvc.net code gives a null ref exception when databainding the list to the jqgrid?
This is a cutdown example to illustrate the problem.
If I change
DataField = "MyClass.Id"
to
DataField = "Id"
It binds just fine, but in my real code I am trying to bind to an object with 2 subobjects and am trying to display data from both on the same grid.
Any suggestions much appreciated.
Thanks
(I saw this post but it didn't get answered: jqgrid List of objects (with sub objects) as datasource)
internal class MyWrapper
{
public MyClass MyClass { get; set; }
public int Id { get; set; }
}
internal class MyClass
{
public int Id { get; set; }
}
public class TestController : Controller
{
public ActionResult Index()
{
return View(GetGrid());
}
public JsonResult SearchGridDataRequested()
{
return GetGrid().DataBind(GetModel().AsQueryable());
}
private JQGrid GetGrid()
{
return new JQGrid
{
ID = "MyGrid",
DataUrl = Url.Action("SearchGridDataRequested"),
Width = Unit.Pixel(700),
Columns = new List<JQGridColumn>
{
new JQGridColumn
{
DataField = "MyClass.Id",
PrimaryKey = true,
DataType = typeof (int)
}
}
};
}
private static IEnumerable<MyWrapper> GetModel()
{
return new List<MyWrapper>
{
new MyWrapper {Id = 1, MyClass = new MyClass {Id = 11}},
new MyWrapper {Id = 2, MyClass = new MyClass {Id = 12}},
new MyWrapper {Id = 3, MyClass = new MyClass {Id = 13}}
};
}
}