I want to change status on my order.

My code

var newOrderStatus = OrderStatus.All().Single(x => x.Name == statusName);
var orderService = ObjectFactory.Instance.Resolve<IOrderService>();
orderService.ChangeOrderStatus(order, newOrderStatus);

newOrderStatus, order & orderService look fine. What am I doing wrong?

I get this error:

NHibernate.PropertyValueException was unhandled by user code
  HResult=-2146232832
  Message=not-null property references a null or transient value UCommerce.EntitiesV2.OrderStatusAudit.NewOrderStatus
  Source=NHibernate
  EntityName=UCommerce.EntitiesV2.OrderStatusAudit
  PropertyName=NewOrderStatus
  StackTrace:
       at NHibernate.Engine.Nullability.CheckNullability(Object[] values, IEntityPersister persister, Boolean isUpdate)
       at NHibernate.Event.Default.AbstractSaveEventListener.PerformSaveOrReplicate(Object entity, EntityKey key, IEntityPersister persister, Boolean useIdentityColumn, Object anything, IEventSource source, Boolean requiresImmediateIdAccess)
       at NHibernate.Event.Default.AbstractSaveEventListener.SaveWithGeneratedId(Object entity, String entityName, Object anything, IEventSource source, Boolean requiresImmediateIdAccess)
       at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.SaveWithGeneratedOrRequestedId(SaveOrUpdateEvent event)
       at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.EntityIsTransient(SaveOrUpdateEvent event)
       at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.OnSaveOrUpdate(SaveOrUpdateEvent event)
       at NHibernate.Impl.SessionImpl.FireSaveOrUpdate(SaveOrUpdateEvent event)
       at NHibernate.Impl.SessionImpl.SaveOrUpdate(String entityName, Object obj)
       at NHibernate.Engine.Cascade.CascadeToOne(Object parent, Object child, IType type, CascadeStyle style, Object anything, Boolean isCascadeDeleteEnabled)
       at NHibernate.Engine.Cascade.CascadeCollectionElements(Object parent, Object child, CollectionType collectionType, CascadeStyle style, IType elemType, Object anything, Boolean isCascadeDeleteEnabled)
       at NHibernate.Engine.Cascade.CascadeCollection(Object parent, Object child, CascadeStyle style, Object anything, CollectionType type)
       at NHibernate.Engine.Cascade.CascadeOn(IEntityPersister persister, Object parent, Object anything)
       at NHibernate.Event.Default.AbstractFlushingEventListener.CascadeOnFlush(IEventSource session, IEntityPersister persister, Object key, Object anything)
       at NHibernate.Event.Default.AbstractFlushingEventListener.PrepareEntityFlushes(IEventSource session)
       at NHibernate.Event.Default.AbstractFlushingEventListener.FlushEverythingToExecutions(FlushEvent event)
       at NHibernate.Event.Default.DefaultFlushEventListener.OnFlush(FlushEvent event)
       at NHibernate.Impl.SessionImpl.Flush()
       at UCommerce.Transactions.OrderService.ChangeOrderStatus(PurchaseOrder purchaseOrder, OrderStatus newOrderStatus, String userName)
       at Weheart.Print.ChangeOrderStatus(PurchaseOrder order, String statusName) in c:\bastard\Bastard\weheart\Print.cs:line 247
       at Weheart.Print.SendOrders() in c:\bastard\Bastard\weheart\Print.cs:line 107
       at Bastard.Handler.ProcessRequest(HttpContext context) in c:\bastard\Bastard\Testing.ashx.cs:line 20
       at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
       at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
  InnerException: