DataGridView不能被LINQ to SQL对象填充

我试图使用下面的代码在我的WinForms应用程序(dgvOrderSizes)上填充DataGridView。如代码中所述，如果我将cod分配给我的DataGridView，它会填充得很好，但是当我尝试将orderDetails分配给它时，它不会填充。我试着调试代码，发现DataSource属性被正确分配，所以我想知道为什么网格没有被填充?(没有异常)

    protected void ShowOrderDetails(int orderNo)
    {
        this.dgvOrderSizes.DataSource = null;
        var cod = from orderDetail in db.OrderDetails
                                 where orderDetail.OrderNo == orderNo
                                 select orderDetail;
        //this.dgvOrderSizes.DataSource = cod;        //works until here

        var orderDetails = from pOrder in cod.AsEnumerable()
                                 select new { pOrder.Plies, pOrder.Composition, pOrder.Size, pOrder.UnitName, pOrder.Quantity, pOrder.Rate, pOrder.ProductionUnitName, pOrder.DeliveryUnitName };
        this.dgvOrderSizes.DataSource = orderDetails;       //doesn't work
    }