private OperationResponse ItemOperationSetProperties(Item item, SetProperties operation, SendParameters sendParameters)
        {
            MethodReturnValue result = this.CheckAccess(item);
            if (result.IsOk)
            {
                item.SetProperties(operation.PropertiesSet, operation.PropertiesUnset);
                var eventInstance = new ItemPropertiesSet
                    {
                        ItemId = item.Id,
                        PropertiesRevision = item.PropertiesRevision,
                        PropertiesSet = operation.PropertiesSet,
                        PropertiesUnset = operation.PropertiesUnset
                    };

                var eventData = new EventData((byte)EventCode.ItemPropertiesSet, eventInstance);
                sendParameters.ChannelId = Settings.ItemEventChannel;
                var message = new ItemEventMessage(item, eventData, sendParameters);
                item.EventChannel.Publish(message);

                // no response sent
                operation.OnComplete();
                return null;
            }

            return operation.GetOperationResponse(result);
        }
        /// <summary>
        /// Handles operation SetProperties: Sets the Item.Properties of an Item and ultimately sends event ItemPropertiesSet to other clients.
        /// </summary>
        public OperationResponse OperationSetProperties(PeerBase peer, OperationRequest request, SendParameters sendParameters)
        {
            var operation = new SetProperties(peer.Protocol, request);
            if (!operation.IsValid)
            {
                return new OperationResponse(request.OperationCode) { ReturnCode = (int)ReturnCode.InvalidOperationParameter, DebugMessage = operation.GetErrorMessage() };
            }

            operation.OnStart();
            Item item;
            if (string.IsNullOrEmpty(operation.ItemId))
            {
                item = this.Avatar;

                // set return values
                operation.ItemId = item.Id;
            }
            else if (this.TryGetItem(operation.ItemId, out item) == false)
            {
                return operation.GetOperationResponse((int)ReturnCode.ItemNotFound, "ItemNotFound");
            }

            return this.ItemOperationSetProperties(item, operation, sendParameters);
        }