What's new in QuickOPC 2020.3

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See also: Versions; Previous version: What's new in QuickOPC 2020.2

Internal version number: 5.59

Key changes:

  • Usability improvements
  • OPC DA under .NET Core on Windows


  • Operating systems: Windows 10 versions supported are now 1803 - 20H2.
  • Visual Studio 2017 is no longer among primary development tools. We expect it to work well for most tasks, but we do not test for that.
  • It is now possible to use OPC DA under .NET Core on Windows (previously, OPC DA was only available under .NET Framework or from COM).


  • For .NET Standard, now using OPC Foundation UA-.NETStandard 1.4.363.107.
  • Updated to BoxedApp SDK 2020.5.


  • Improved the licensing error messages. Besides more precise wording, the typical messages now contain the list of (serial numbers of) licenses that were considered but dropped, together with their "release date covered" field, which is frequently the cause for the license not being recognized.
  • Added text to License Manager dialog, explaining that licenses with Active status are not necessarily valid, depending on the particular combination of the component and environment status, and that the capabilities of the component itself should be used to check the license validity.
  • Starting with build 5.59.1055.1, the license keys are properly recognized on computers with Windows FIPS mode enabled.


  • Added a new assembly OpcLabs.DotProlog to the product. It is needed whenever you use OpcLabs.BaseLibForms or OpcLabs.EasyOpcForms assemblies, but it does not need to be referenced in your project.
  • Modified the NuGet manifest so that under .NET Framework, the packages for .NET Standard are not unnecessarily considered as dependencies.
  • Fixed the version in dependency on Microsoft Visual C++ Redistributables. The proper dependency is "Microsoft Visual C++ Redistributable for Visual Studio 2015, 2017 and 2019", from https://support.microsoft.com/en-us/help/2977003/the-latest-supported-visual-c-downloads .
  • Binaries are no longer code-signed with SHA-1 (only SHA-256).

Installation and Uninstallation

  • The setup log file now includes product version and build number information.

Component Improvements

  • Input arguments that are materialized sequences (such as arrays, collections and lists) are now consistently checked for nullness of their elements before a method body is executed. That is, if the developer mistakenly passes in a sequence with a null element into an argument where it is not allowed, an ArgumentNullException exception will always be thrown upon method entry, and with an improved error text indicating the position (index) of the offending element.

OPC Classic

  • Added method IEasyDAClient.GetItemSubscriptionArguments. This method allows the developer to obtain the arguments used to make an item subscription.
  • Added method IEasyAEClient.GetEventsSubscriptionArguments. This method allows the developer to obtain the arguments used to make events subscription.
  • Added an overload of IEasyDAClient.ChangeItemSubscription extension method, with an argument of type DAHandleGroupArguments.
  • Added explicit conversion operator from DAVtqResult to ValueResult and their generic (typed) variants. Same functionality has the static DAVtqResult.ToValueResult method (for programming languages that do not support explicit conversion operators).
  • Large OPC-DA requests are now "chunked", i.e. divided into smaller requests and performed sequentially. This is beneficial especially with Subscribe and Unsubscribe requests, because with many OPC servers, it allows the results be served to the client sooner. The behavior (chunk sizes, and whether the chunking will be applied to specific operation types at all) is configurable, and is managed by the new OPC-DA Optimizer plugin.
  • Calls to OPC Read, Write and GetProperty operations that contain identical (except for the State property) arguments are now merged to perform just a single Read, Write or GetProperty (request merging). This behavior can be turned off in the OPC-DA Optimizer plugin parameters.
  • Added (extension) method IEasyDAClient.WaitForMultipleItems. Subscribes to the specified OPC-DA items, and monitors their data until the predicates specified for each item become true, an error occurs, or the alloted time elapses.
  • Added (extension) method IEasyDAClient.WaitForMultipleItemValues. Subscribes to the specified OPC-DA items, and monitors their data until they have at least the quality specified for each item, an error occurs, or the alloted time elapses.
  • Added (extension) method IEasyDAClient.WaitForItemValue. Subscribes to the specified OPC-DA item, and monitors its data until it has "good" quality, an error occurs, or the alloted time elapses.
  • Added (extension) methods IEasyDAClient.SupportsTechnology and IEasyAEClient.SupportsTechnology. Determines whether the client object supports a given OPC technology or technologies (such as OPC COM or OPC XML).
  • The DANodeElementCollection and DAPropertyElementCollection classes now implement the ICloneable interface.
  • The AEAttributeElementCollection, AECategoryElementCollection, AEConditionElementCollection and AENodeElementCollection classes now implement the ICloneable interface.


  • Added HasServerTimestamp and HasSourceTimestamp properties to the UADataValue class (and therefore, also to the derived UAAttributeData and UADataSetFieldData classes). These properties determine whether there is a (non-default) server or source timestamp in the data value.
  • Added method IEasyUAClient.IsKnownMonitoredItemSubscriptionHandle. Determines whether the given monitored item subscription handle is known to the given client.

OPC UA Client-Server

  • Added TestEndpoint extension method on IEasyUAClient. The method tests whether an operational connection can be established to the specified endpoint of an OPC UA server.
  • Added explicit conversion operator from UAAttributeDataResult to ValueResult and their generic (typed) variants. Same functionality has the static UAAttributeData.ToValueResult method (for programming languages that do not support explicit conversion operators).
  • For consistency, renamed the Uri property in the ResourceDescriptor class to Url (in line with its UrlString property). All derived classes are of course also affected - including ServerDescriptor and UAEndpointDescriptor.


  • Added method IEasyUASubscriber.IsKnownDataSetSubscriptionHandle. Determines whether the given data set subscription handle is known to the given subscriber.
  • Added TestConnection and TestConnectionAsync methods on IEasyUASubscriber. The methods test whether an OPC UA PubSub connection can be successfully established.
  • Added TestSubscription and TestSubscriptionAsync methods on IEasyUASubscriber. The methods test whether an OPC UA PubSub subscription can be successfully established.
  • Factored out base UADataSetHeader class from the UADataSetData class. The UADataSetHeader can be used e.g. to distinguish dataset data that represent different datasets.
  • Added Logicalize method to several PubSub objects (descriptors). The method removes the physical information from the object.
  • Added AllowsResolution property to several PubSub objects (descriptors). The property determines whether the object has the necessary information to allow logical resolution..
  • Added HasConfigurationVersion and HasTimestamp properties to the UADataSetHeader class.
  • Added MajorVersionDateTimeLocal and MinorVersionDateTimeLocal properties to the UAConfigurationVersion class.
  • Accompanied each string-typed XXXXUriString or XXXXUrlString property by a corresponding Uri-typed XXXXUri or XXXXUrl property (only in .NET, because the Uri class is not COM-visible).
  • Based on UA Specification Errata 1.04, the UAPublisherId class no longer allows zero numeric identifiers, or empty string identifiers.

COM Components

  • Added AddRange method to ElasticVector. Among other uses, it can be used in Xojo to convert a keyed collection to an elastic vector, and index its elements by integers, as a workaround for Xojo inability to enumerate the collections using COM interface method GetEnumerator.
  • In COM-visible objects, consistently added SetXXXX methods to accompany each property setter whose argument is System.Object. This allows such properties be set from Visual Basic 6.0 with early binding.
  • For COM tools (such as PHP) that do not allow to navigate between COM interfaces of an object, or provide an "amalgamated" set of members from multiple interfaces, when a specific interface is returned by a property or method, added InteropHelper object with the AsObject method. By passing the object through this method, the consuming COM tool is forced to use late binding, allowing the intended members be accessed.
  • Added AsXXXXDataType methods to the _DataType COM interface, allowing the data type downcasting for tools like PHP.
  • In order to allow passing 'null' to nullable array arguments from VBScript, consistently changed corresponding argument types in COM interfaces from "Type[]" to "object".
  • Added alternative date/time properties to allow milliseconds resolution in VBA in Excel, which removes the sub-seconds parts of VT_DATE values. These new properties use VT_R8 variant type instead, and provide a milliseconds resolution. The properties have the word "Double" added as postfix to their names. Most importantly, in the UADataValue class and its derived classes UAAttributeData and UADataSetFieldData, you can now use the ServerTimestampDouble, ServerTimestampLocalDouble, SourceTimestampDouble and SourceTimestampLocalDouble properties for this purpose. In the DAVtq class, you can now use TimestampDouble and TimestampLocalDouble properties for this purpose. Other affected and enhanced classes with date/time properties are: AEConditionState, AEEventData, UABaseEventObject and UADataSetData.
  • All COM methods that were returning _List now return _ElasticVector (which contains all _List members but does not inherit from it; the returned class, ElasticVector, implements both _List and _ElasticVector). This change has been done to allow languages like Xojo access the _ElasticVector members.

Component Refactorings

OPC Classic

  • The IEasyDAClient.ReadMultipleItemValues and ReadItemValue (extension) methods no longer wait until a "non-bad" value becomes available. Instead, they simply perform a read, and an error is returned if the data do not contain valid value. The new behavior is consistent with corresponding methods in OPC UA, with method names better describing the internal working. This is potentially a breaking change (with some OPC servers). If you want the behavior similar to the past, use the new WaitForMultipleItemValues and WaitForItemValue (extension) methods, described at other place in this article.
  • Moved EnableNativeClient, EnableNetApiClient (and EnableServiceClient, not yet functional) properties from EasyDAClient and EasyDAClientConfiguration classes to EasyDAInstanceParameters class. Besides other advantages, this made them available for configuration in Connectivity Explorer and OpcCmd tools.
  • Harmonized the base exceptions returned, between OPC DA and OPC XML-DA specifications, and also between the native and NET API client implementations. User code can now rely on the fact that the base exception for direct OPC Classic operations will be ExtendedCOMException or its derivation, and that both ErrorCode (HResult) and QualifiedName properties will be filled in, whenever possible. For well-known errors in COM-based OPC DA, the component automatically derives the QualifiedName from the ErrorCode. For well-known errors in OPC XML-DA, the component automatically derives the ErrorCode from the QualifiedName. OPC XML-DA errors are mapped to their corresponding COM-based OPC DA counterparts, if they exist. The same harmonization is now being done also in EasyAEClient, for OPC A&E. Timeout errors that do not come from lower layers will be TimeoutException or its derivation.
  • Parameter bucketing has been reimplemented, and is now available as part of the OPC-DA Optimizer. The PercentDeadbandBucketsPerDecade and UpdateRateBucketsPerDecade properties have been moved to the DAParameterBucketingParameters class. The EasyDATopicParameters.ExactManualGroupMatch property has been removed; use DAOptimizerPluginParameters.EnableParameterBucketing property instead (note the negated semantics though).
  • Item caching has been reimplemented, and is now available as part of the OPC-DA Optimizer. Item caching can be turned off using the DAOptimizerPluginParameters.EnableItemCaching property.
  • Parameter restricting has been reimplemented, and is now available as part of the OPC-DA Optimizer. The related properties have been moved to the DAParameterRestrictingParameters class, and renamed to: FastestUpdateRate, SlowestUpdateRate, LowestPercentDadband, HighestPercentDadband.
  • Auto-subscribing has been reimplemented and improved, and is now available as part of the OPC-DA Optimizer. The related properties are now available in the DAAutoSubscribingParameters class. The auto-subscribing is now turned off by default; set the DAOptimizerPluginParameters.EnableAutoSubscribing property to true to turn it on. Alternatively (for shorter code), use the new TryEnableAutoSubscribingOptimization extension method.
  • Removed properties: EasyDAEngineParameters.ClientLruSize, EasyDAEngineParameters.TopicLruSize, EasyAEEngineParameters.ClientLruSize.
  • The EasyDAClientUpdateRates class, and the EasyDAInstanceParameters.UpdateRates property have been removed. There is no need for them any more in the improved auto-subscribing optimization.
  • Subscription blending has been reimplemented, and is now available as part of the OPC-DA Optimizer. Subscription blending can be turned off using the DAOptimizerPluginParameters.EnableSubscriptionBlending property.
  • Various optimizations (performed by OPC-DA Optimizer) are now done on a specific EasyDAClient instance, and are not shared (global). In applications that currently use separate EasyDAClient instances and can benefit from sharing some optimizations (such as Subscription Blending or Item Caching), consider using a common EasyDAClient instance.
  • Changed the default scheme in ServerDescriptor from "opcda" to "dcom" (but both schemes still work for OPC-DA).


  • Extended some OPC UA error messages with concrete information helpful for troubleshooting.

COM Components

  • All COM methods on the main components (EasyDAClient, EasyAEClient, EasyUAClient, EasyUASubscriber) now pump any available Windows messages upon entry to the method, when the current thread is in a single-threaded apartment (STA). It is a responsibility of the user's code to pump the messages (in an STA), but since developers are not commonly aware of it, this behavior helps to prevent memory leaks in tight loops involving the affected components.

User Interface

  • Added "Server Connection Test" command to context menu on OPC UA endpoint nodes in browsing controls and dialogs. The commands attempts to make a connection to the OPC UA server using the selected endpoint, and displays the outcome. This affects user interface displayed by tools (such as in Live Mapping, or in Connection Explorer), and also the interface to the end user, such as through UAHostAndEndpointDialog, or UABrowseControl components.

Windows Forms Dialogs

  • In dialogs presented by AEAreaOrSouceDialog, DAItemDialog, OpcBrowseDialog, UABrowseDialog and UADataDialog, double-clicking on a list node that is both branch and leaf now closes the dialog, as if "OK" was pressed with focus on that node. Previously, doing so would open the node in the tree view. This behavior change also applies to the point browsing dialog in Connectivity Model (such as when selecting points for Live Binding), which is not available for programmatic usage.

Windows Forms Controls

  • Added general AutomaticValueControl, which provides "control pages" for various objects, based on specified object type, and criteria such as whether the control should be nullable, polymorphic, or read-write.
  • Control pages (usable by AutomaticValueControl) made available for following OPC UA PubSub configuration objects: UASubscribeDataSetArguments, UASubscribeDataSetFilter, UADataSetSubscriptionDescriptor, UAPubSubConnectionDescriptor, UASubscriberCommunicationParameters.
  • Added specialized controls for several OPC UA PubSub objects: UAVersionTimeControl, UAFieldDataDictionaryControl, UADataSetHeaderControl and UADataSetDataControl.


OPC Classic

  • The EasyDAClient and EasyAEClient now have static LogEntry event, and the (non-static) LogEntry event on EasyDAClientConfiguration and EasyAEClientConfiguration is now functional. The semantics is analogous to the LogEntry event on EasyUAClient or EasyUAClientConfiguration. Currently, events related to licensing, callback errors and queue overflows are reported. When extended tracing is enabled, log entries appear in the generated trace.

Tools and Online Services

Demo Servers and Publishers

  • The simulation server for OPC DA now provides initial values also for Simulation.Register_ArrayOfXXXX items (previously, these items returned an error initially, and required an external "write" for them to return a valid value). The initial value is always an empty array.

Connectivity Explorer

  • Log entries from EasyDAClient now appear in "Event Records" view.
  • Added Advanced tab to OPC-UA Attribute Point Subscribe Parameters editor. Allows the user to view and modify advanced monitoring parameters ("Queue size" and "Discard oldest") and subscription parameters ("Publishing interval" and "Priority").
  • Added Edit tab to OPC-UA Attribute Point Read Parameters editor. Allows the user to view and modify the "Maximum age" and "Value only" parameters.
  • Added Edit tab to OPC-UA Attribute Point Write Parameters editor. Allows the user to view and modify the "Value type code" and "Value only" parameters.
  • Added Edit tab to OPC-DA Item Point Read Parameters editor. Allows the user to view and modify the "Data source", "Value age" and "Value only" parameters.
  • Added Edit tab to OPC-DA Item Point Write Parameters editor. Allows the user to view and modify the "Value only" parameter.


  • The OPC Kit Server (OPC DA and OPC A&E simulation server) is now also available separately as a zipped file under Tool Downloads.
  • ComCreateTest, a tool for quick (local) instantiation test of OPC "Classic" servers under 32-bit or 64-bit environments has been made available under Tool Downloads.


  • Visual Studio example projects are now being maintained with Visual Studio 2019.
  • For better optimization, changed Web-based examples (C#, VB.NET) to use a shared client instance.

Platform: COM

  • Added VBA example in Excel: UACallMethodNoArguments.xlsm. Shows how to call OPC UA methods that have no arguments. Shows how to disable or enable OPC UA condition.
  • Added Xojo example for OPC Data Access: Read multiple items.
  • Retested the Xojo examples with Xojo 2019r3.1 and Xojo 2020r1.2.

OPC Classic

  • Added larger number of C# examples, showing e.g. how to browse access paths, browse branches, browse leaves, browse properties, browse servers, read item value with specifying server's CLSID, read multiple items "from device", do many reads repeatedly, perform synchronous OPC read, read multiple item values, unsubscribe all or multiple items, write an item (including timestamp and quality), list OPC categories that the server implements, and more.
  • Added C# FormsDocExamples project, with examples for user interface (showing various browsing dialogs for OPC Classic), and added these C# examples to conceptual&reference documentation.
  • Added call to TryEnableAutoSubscribingOptimization to (C#, VB.NET) Web-based examples, to show how to enable the auto-subscribing optimization.

OPC UA Client-Server

  • Added a WPF port of OPC UA Demo Application: WpfEasyOpcUADemo. This new project is available both as a pre-built application that you can run after product install, and in source form in the C# examples solution.
  • Added pair of examples UAWcfService1 and UAWcfClient1 (C#): A simple Web service using WCF technology. Provides a GetData method to read a value of an OPC UA variable. Accompanied by a console-based client code.
  • Added example UAWindowsService1 (C#): A Windows Service that subscribes to variables from the OPC UA sample server, and logs their changes into a file.
  • Added C# example that shows how to read value of server's NamespaceArray, and display the namespace URIs in it.
  • Added C# example that shows how to write an ever-incrementing value to an OPC UA variable.
  • Added C# UAFormsDocExamples project, with examples for user interface (showing various browsing dialogs for OPC UA), and added these C# examples to conceptual&reference documentation.
  • Added C# example that shows how to read a state of an alarm in OPC UA Alarms & Conditions.
  • Added C# example that shows how to use multi-select with UADataDialog.


  • Added Windows Forms demo application for OPC UA PubSub (EasyOpcUAPubSubDemo) in C#. Project source code is available in the Examples solution, and compiled version of the application is installed by the Setup program. The application offers a selection of ready-made settings for various OPC UA PubSub subscription choices, and also offers a rich user interface to specify custom settings. It then allows to subscribe to datasets and display the received data dynamically.

Documentation and Help

  • Documentation is no longer provided in the booklet (PDF) form.
  • Made clear at multiple places that Product Option licenses (such as Excel Option or StreamInsight Option) require base product license first.
  • Added a chapter documenting the existence of multiple implementations (native and NET API client for OPC Data Access), their capabilities, and how to enable and disable them.
  • Improvements in the Best Practices section.

COM Components

  • Documentation for all COM objects now consistently contains "Object Creation" section, with syntax for object creation in following languages or tools: C++, Free Pascal, JScript, Object Pascal (Delphi), Perl, PHP, PowerScript, Python, REALbasic (Xojo), Visual Basic (VB 6.), Visual FoxPro, VBA, VBScript, Xbase++.
  • Added explanation of Xojo programming specifics, explaining how to use the ElasticVector for enumeration of keyed collections.