public async Task VectorAdd()
        {
            var channel = new UaTcpSessionChannel(
                this.localDescription,
                this.certificateStore,
                new AnonymousIdentity(),
                "opc.tcp://*****:*****@"  ------------------");
            Console.WriteLine($"  {result}");

            Console.WriteLine($"Closing session '{channel.SessionId}'.");
            await channel.CloseAsync();

            result.Z
            .Should().Be(6.0);
        }
        public async Task ReadHistoryRawValues()
        {
            // describe this client application.
            var clientDescription = new ApplicationDescription
            {
                ApplicationName = "Workstation.UaClient.FeatureTests",
                ApplicationUri  = $"urn:{System.Net.Dns.GetHostName()}:Workstation.UaClient.FeatureTests",
                ApplicationType = ApplicationType.Client
            };

            // place to store certificates
            var certificateStore = new DirectoryStore("./pki");

            // create a 'UaTcpSessionChannel', a client-side channel that opens a 'session' with the server.
            var channel = new UaTcpSessionChannel(
                clientDescription,
                certificateStore,
                new AnonymousIdentity(),      // the anonymous identity
                "opc.tcp://localhost:48010"); // the endpoint of Unified Automation's UaCPPServer.

            try
            {
                // try opening a session and reading a few nodes.
                await channel.OpenAsync();

                Console.WriteLine($"Opened session with endpoint '{channel.RemoteEndpoint.EndpointUrl}'.");
                Console.WriteLine($"SecurityPolicy: '{channel.RemoteEndpoint.SecurityPolicyUri}'.");
                Console.WriteLine($"SecurityMode: '{channel.RemoteEndpoint.SecurityMode}'.");
                Console.WriteLine($"UserIdentityToken: '{channel.UserIdentity}'.");

                Console.WriteLine("\nCheck if DataLogger active.");

                // check if DataLoggerActive is true. If not, then call method StartLogging.
                var req = new ReadRequest
                {
                    NodesToRead = new[] {
                        new ReadValueId {
                            NodeId = NodeId.Parse("ns=2;s=Demo.History.DataLoggerActive"), AttributeId = AttributeIds.Value
                        }
                    },
                };
                var res = await channel.ReadAsync(req);

                if (StatusCode.IsBad(res.Results[0].StatusCode))
                {
                    throw new InvalidOperationException("Error reading 'Demo.History.DataLoggerActive'. ");
                }
                var isActive = res.Results[0].GetValueOrDefault <bool>();

                if (!isActive)
                {
                    Console.WriteLine("Activating DataLogger.");

                    var req1 = new CallRequest
                    {
                        MethodsToCall = new[] {
                            new CallMethodRequest {
                                ObjectId = NodeId.Parse("ns=2;s=Demo.History"), // parent node
                                MethodId = NodeId.Parse("ns=2;s=Demo.History.StartLogging")
                            },
                        },
                    };
                    var res1 = await channel.CallAsync(req1);

                    if (StatusCode.IsBad(res1.Results[0].StatusCode))
                    {
                        throw new InvalidOperationException("Error calling method 'Demo.History.StartLogging'.");
                    }
                    Console.WriteLine("Note: Datalogger has just been activated, so there will be little or no history data to read.");
                    Console.WriteLine("      Try again in 1 minute.");
                }

                Console.WriteLine("\nReading history for last 1 minute(s).");

                // A continuation point is returned if there are more values to return than the
                // limit set by parameter NumValuesPerNode. A client should continue calling HistoryRead
                // until the continuation point returns null.
                byte[] cp = null;

                do
                {
                    var req2 = new HistoryReadRequest
                    {
                        HistoryReadDetails = new ReadRawModifiedDetails
                        {
                            StartTime        = DateTime.UtcNow.Add(TimeSpan.FromSeconds(-60)), // set start time to 1 minute ago
                            EndTime          = DateTime.UtcNow,
                            NumValuesPerNode = 100,                                            // sets limit. if there are more values to return then a continuation point is returned.
                            ReturnBounds     = false,                                          // set true to return interpolated values for the start and end times
                        },
                        TimestampsToReturn        = TimestampsToReturn.Both,
                        ReleaseContinuationPoints = false, // set true to abandon returning any remaining values from this interval
                        NodesToRead = new[] {
                            new HistoryReadValueId {
                                NodeId = NodeId.Parse("ns=2;s=Demo.History.DoubleWithHistory"), ContinuationPoint = cp
                            },
                        },
                    };

                    var res2 = await channel.HistoryReadAsync(req2);

                    if (StatusCode.IsGood(res2.Results[0].StatusCode))
                    {
                        var historyData = res2.Results[0].HistoryData as HistoryData;

                        Console.WriteLine($"Found {historyData.DataValues.Length} value(s) for node '{req2.NodesToRead[0].NodeId}':");

                        foreach (var dv in historyData.DataValues)
                        {
                            Console.WriteLine($"Read {dv.Value}, q: {dv.StatusCode}, ts: {dv.SourceTimestamp}");
                        }

                        cp = res2.Results[0].ContinuationPoint;
                        // if ContinuationPoint is null, then there is no more data to return.
                        if (cp == null)
                        {
                            break;
                        }
                    }
                    else
                    {
                        Console.WriteLine($"HistoryRead return statuscode: {res2.Results[0].StatusCode}");
                        break;
                    }
                } while (cp != null); // loop while ContinuationPoint is not null.

                Console.WriteLine($"\nClosing session '{channel.SessionId}'.");
                await channel.CloseAsync();
            }
            catch (Exception ex)
            {
                await channel.AbortAsync();

                Console.WriteLine(ex.Message);
            }
        }
        public async Task VectorAdd()
        {
            // describe this client application.
            var clientDescription = new ApplicationDescription
            {
                ApplicationName = "Workstation.UaClient.FeatureTests",
                ApplicationUri = $"urn:{System.Net.Dns.GetHostName()}:Workstation.UaClient.FeatureTests",
                ApplicationType = ApplicationType.Client
            };

            // place to store certificates
            var certificateStore = new DirectoryStore("./pki");

            // create a 'UaTcpSessionChannel', a client-side channel that opens a 'session' with the server.
            var channel = new UaTcpSessionChannel(
                clientDescription,
                certificateStore,
                new AnonymousIdentity(), // the anonymous identity
                "opc.tcp://*****:*****@"  ------------------");
                Console.WriteLine($"  {result}");

                Console.WriteLine($"\nClosing session '{channel.SessionId}'.");
                await channel.CloseAsync();
            }
            catch (Exception ex)
            {
                await channel.AbortAsync();
                Console.WriteLine(ex.Message);
            }
        }