.NET and Python Development

Different product versions can be installed on the same computer in parallel. For example, version 5.12 can be installed together with version 5.02 or even version 3.03.

The above rule only applies to the effects of the installation on the target system using the Setup Program – things like Start menu folders and shortcuts, files installed into the Program files directory, etc. As to the actual component assemblies in .NET, you can have many versions and even different builds and revisions on the same computer, and they will all work in mutual isolation.

There can be only one version of QuickOPC Visual Studio extension installed into Visual Studio at a time, and if you are using it, it has to match the OPC Data Client version you are developing for precisely.

Simulation OPC Server

The simulation OPC server (for OPC “Classic”) is not subject to the versioning rules described above for the OPC Data Client product. Just one instance of simulation OPC server can exist on a computer. Features are being added to the simulation OPC server with newer versions of OPC Data Client. Always install the simulation OPC server from the latest OPC Data Client version in order to guarantee that all examples are functional.

COM Development

GUIDs of OPC Data Client COM components do not change between versions, but their API may change. For COM tools that use early binding, such as Object Pascal (Delphi), Free Pascal, or Visual C++, this has following consequences:

• For BUILDING the application, you can have multiple versions of OPC Data Client installed on one computer, and *without uninstalling/reinstalling*, you can properly build for the proper version. The version for which you build is determined by the version of OPC Data Client type libraries you use. You can select any installed version, and when you build with the source files generated from the specific version of type libraries, you will end up with your application tied to that version of OPC Data Client.

• For RUNNING the (COM) applications, you can only run one OPC Data Client version on the computer. If the application OPC Data Client version would not match the installed OPC Data Client version, it may crash, or malfunction in some other way. When doing multiple OPC Data Client installs on the computer, the latest one *wins*. More precisely, what matters is the latest version of OPC Data Client assemblies registered for COM interop – which is what the installation does automatically.

For most COM tools that use late binding (such as PHP, VBA, VBScript and others), there is no "building" step. The COM code that uses OPC Data Client will work with different versions as long as the API exposed by OPC Data Client has not changed (such as method that has been renamed, or aguments of a method have been rearranged). Still, only one OPC Data Client version can run on the computer.