I have a web service and I'm experiencing a strange exception:

System.InvalidOperationException: Unable to change command: it is already prepared
   at Xtensive.Orm.Providers.Command.AddPart(CommandPart part)
   at Xtensive.Orm.Providers.BatchingCommandProcessor.Xtensive.Orm.Providers.ISqlTaskProcessor.ProcessTask(SqlLoadTask task)
   at Xtensive.Orm.Providers.BatchingCommandProcessor.ExecuteBatch(Int32 numberOfTasks, QueryRequest lastRequest)
   at Xtensive.Orm.Providers.SqlSessionHandler.ExecuteQueryTasks(IEnumerable`1 queryTasks, Boolean allowPartialExecution)
   at Xtensive.Orm.Session.ProcessDelayedQueries(Boolean allowPartialExecution)
   at Xtensive.Orm.Internals.Prefetch.Fetcher.ExecuteTasks(IEnumerable`1 containers, Boolean skipPersist)
   at Xtensive.Orm.Internals.Prefetch.PrefetchManager.ExecuteTasks(Boolean skipPersist)
   at Xtensive.Orm.Providers.SqlSessionHandler.FetchEntityState(Key key)
   at Xtensive.Orm.QueryEndpoint.SingleOrDefault(Key key)
   at Xtensive.Orm.Internals.FieldAccessors.EntityFieldAccessor`1.GetValue(Persistent obj)
   at Xtensive.Orm.Persistent.GetFieldValue[T](FieldInfo field)
   at Quadra.WMS.BusinessLogic.Place.get_FullName()
   at System.Linq.Enumerable.WhereSelectListIterator`2.MoveNext()
   at System.String.Join(String separator, IEnumerable`1 values)
   at Quadra.WMS.BusinessLogic.Connector1C.DoUpdateAddress(Int32 skuId, IEnumerable`1 places)

Quadra.WMS.BusinessLogic.Place.get_FullName is in this code:

public class Place : Entity
{
    public Place(Session session) : base(session)
    {
    }

    [Key]
    [Field]
    public int Id { get; set; }

    [Field]
    public string Name { get; set; }

    [Field]
    public Barcode Barcode { get; set; }

    [Field]
    public Place ParentPlace { get; set; }

    public string FullName
    {
        get
        {
            var placeList = new List<string>();
            var p = this;
            while (p != null)
            {
                placeList.Add(p.Name);
                p = p.ParentPlace;
            }
            return string.Join(" / ", Enumerable.Reverse(placeList));
        }
    }
}

FullName should return a string of a full path of the place and its parent places. I'm using 5.0-beta1 version.