private OperationResponse ItemOperationAttachInterestArea(
            Item item, AttachInterestArea operation, InterestArea interestArea, SendParameters sendParameters)
        {
            if (item.Disposed)
            {
                return operation.GetOperationResponse((int)ReturnCode.ItemNotFound, "ItemNotFound");
            }

            lock (interestArea.SyncRoot)
            {
                interestArea.Detach();
                interestArea.AttachToItem(item);
                interestArea.UpdateInterestManagement();
            }

            // use item channel to ensure that this event arrives before any move or subscribe events
            OperationResponse response = operation.GetOperationResponse(MethodReturnValue.Ok);
            sendParameters.ChannelId = Settings.ItemEventChannel;
            this.Peer.SendOperationResponse(response, sendParameters);

            operation.OnComplete();
            return null;
        }
        /// <summary>
        /// Handles operation AttachInterestArea: Attaches an existing InterestArea to an existing Item.
        /// </summary>
        public OperationResponse OperationAttachInterestArea(PeerBase peer, OperationRequest request, SendParameters sendParameters)
        {
            var operation = new AttachInterestArea(peer.Protocol, request);
            if (!operation.IsValid)
            {
                return new OperationResponse(request.OperationCode) { ReturnCode = (int)ReturnCode.InvalidOperationParameter, DebugMessage = operation.GetErrorMessage() };
            }

            operation.OnStart();
            InterestArea interestArea;
            if (this.TryGetInterestArea(operation.InterestAreaId, out interestArea) == false)
            {
                return operation.GetOperationResponse((int)ReturnCode.InterestAreaNotFound, "InterestAreaNotFound");
            }

            Item item;
            bool actorItem;
            if (string.IsNullOrEmpty(operation.ItemId))
            {
                item = this.Avatar;
                actorItem = true;

                // set return vaues
                operation.ItemId = item.Id;
            }
            else
            {
                actorItem = this.TryGetItem(operation.ItemId, out item);

            }

            if (actorItem)
            {
                // we are already in the item thread, invoke directly
                return this.ItemOperationAttachInterestArea(item, operation, interestArea, sendParameters);
            }
            else
            {
                // search world cache just to see if item exists at all
                if (this.World.ItemCache.TryGetItem(operation.ItemId, out item) == false)
                {
                    return operation.GetOperationResponse((int)ReturnCode.ItemNotFound, "ItemNotFound");
                }
                else
                {
                    // second parameter (peer) allows us to send an error event to the client (in case of an error)
                    item.Fiber.Enqueue(() => this.ExecItemOperation(() => this.ItemOperationAttachInterestArea(item, operation, interestArea, sendParameters), sendParameters));

                    // response is sent later
                    return null;
                }
            }
        }