/// <summary>
        /// Search cached query for all active nodeId of all servers in topology.
        /// Add new nodes to station topology.
        /// </summary>
        /// <param name="fullQuery">A cached query</param>
        /// <param name="topologyStations">List of stations in topology</param>
        private async Task AddNewNodes(RDXCachedAggregatedQuery fullQuery, List <string> topologyStations)
        {
            List <string> opcUaServers = fullQuery.GetActiveServerList();

            foreach (string opcUaServer in opcUaServers)
            {
                ContosoOpcUaServer topologyNode = _topology[opcUaServer.ToLower()] as ContosoOpcUaServer;
                if (topologyNode != null)
                {
                    List <string> topologyNodeIdList = topologyNode.NodeList.Select(x => x.NodeId).ToList();
                    List <string> activeNodeIdList   = fullQuery.GetActiveNodeIdList(opcUaServer);
                    var           newNodeIdList      = activeNodeIdList.Except(topologyNodeIdList, StringComparer.InvariantCultureIgnoreCase);
                    if (newNodeIdList.Count() > 0)
                    {
                        RDXOpcUaQueries opcUaQueries = new RDXOpcUaQueries(CancellationToken.None);
                        foreach (string newNodeId in newNodeIdList)
                        {
                            RDXTrace.TraceInformation("RDX Worker adding node {0} to server {1}", newNodeId, opcUaServer);
                            string symbolicName = await opcUaQueries.QueryDisplayName(DateTime.UtcNow, opcUaServer, newNodeId);

                            topologyNode.AddOpcServerNode(
                                newNodeId,
                                symbolicName,
                                null,
                                ContosoOpcNodeOpCode.Avg,
                                null,
                                true,
                                null,
                                null,
                                null,
                                null,
                                null,
                                null,
                                null
                                );
                        }
                    }
                }
            }
        }