The only reason I can think of is that an entity is added individually to the UoW for saving and is also present in a collection which has been added for saving. Could you check that for me please? I'll see if I can harden the code a bit against that particular scenario, as looking at the code, it seems to me that's the only possible cause of it:
/// <summary>
/// Constructs the save process queues for insert and update actions. These queues are constructed from the entities added to this UoW
/// for save either individually or in a collection. Call this method to determine what the sequence will be for the insert and update
/// actions executed during Commit(). Commit() uses this method as well as well as the serialization/deserialization logic, to avoid
/// sending large object graphs with few changes.
/// </summary>
public void ConstructSaveProcessQueues()
{
// clear current queues
_entitiesToInsert = new ArrayList(_entitiesToSave.Count);
_entitiesToUpdate = new ArrayList(_entitiesToSave.Count);
Hashtable inProcess = new Hashtable(512);
Hashtable recursed = new Hashtable(512);
Hashtable inQueue = new Hashtable(512);
Hashtable postponed = new Hashtable(512);
// some entities are added for recursive saves, others aren't. Use a per-entity queue build action.
ObjectGraphUtils graphUtils = new ObjectGraphUtils();
ArrayList elementsToProcess = new ArrayList(_entitiesToSave);
Hashtable tmpObjectIDsToSave = new Hashtable(_objectIDsToSave);
foreach(UnitOfWorkCollectionElement2 currentElement in _collectionsToSave)
{
foreach(IEntity2 currentEntity in currentElement.Collection)
{
if(!tmpObjectIDsToSave.ContainsKey(currentEntity.ObjectID))
{
UnitOfWorkElement2 newElement = new UnitOfWorkElement2(currentEntity, null, currentElement.Refetch, currentElement.Recurse);
tmpObjectIDsToSave.Add(currentEntity.ObjectID, newElement);
elementsToProcess.Add(newElement);
}
}
}
foreach(UnitOfWorkElement2 element in elementsToProcess)
{
if(element.Recurse)
{
graphUtils.DetermineActionQueues(element.Entity, element.Restriction, ref _entitiesToInsert, ref _entitiesToUpdate, ref inProcess,
ref recursed, ref inQueue, ref postponed, element.Refetch);
}
else
{
if(element.Entity.IsNew)
{
_entitiesToInsert.Add(new ActionQueueElement(element.Entity, null, element.Refetch));
}
else
{
if(element.Restriction!=null)
{
_entitiesToUpdate.Add(new ActionQueueElement(element.Entity, element.Restriction, element.Refetch));
}
else
{
_entitiesToUpdate.Add(new ActionQueueElement(element.Entity, element.Entity.GetConcurrencyPredicate(ConcurrencyPredicateType.Save), element.Refetch));
}
}
inQueue.Add(element.Entity.ObjectID, null); // <<<<<< here it can go wrong
}
}
}
You should see it in a minute or so.