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Marc SchierandCopilot
0383472ebc
### Summary Three related gaps mean no `PublishedDataSet` can produce a message that is not a key frame or a derived delta frame. `PubSubDataSetMessageType.Event` and the `ua-event` wire tag of Part 14 §7.2.5.4 are modelled but unreachable. This PR also corrects the JSON `DataValue` status member to the Part 6 Table 42 name `Status`. ### 1. A dataset cannot declare what its sample is `PublishedDataSetSnapshot` carries a metadata version, fields and a timestamp. `WriterGroup.BuildDataSetMessageAsync` therefore decides the message kind alone: `KeyFrameCount <= 1` forces `KeyFrame`, otherwise it derives a delta by comparing the snapshot **positionally** against the previous one. That derivation assumes successive snapshots describe the same fields in the same order, which holds only for a source returning its complete current state every cycle. A source whose samples are *occurrences* — an event, a condition snapshot, or a delta it has already computed — cannot satisfy it: consecutive samples carry different fields, so field *i* of one occurrence is compared against field *i* of an unrelated earlier one, and `Math.Min` silently truncates when the counts differ. `PublishedDataSetSnapshot` now carries an optional `MessageType`. When set, the writer publishes exactly the supplied fields under the declared type and leaves its key-frame state untouched. When null — the default, and every existing caller — behaviour is unchanged. ### 2. The event writer was unreachable `EventDataSetWriter` and `EventPublishedDataSet` implement the Part 14 §6.2.4 event model correctly, but nothing could use them: - `EventPublishedDataSet` did not implement `IPublishedDataSet`, so `PubSubApplication` could not register an event dataset; - nothing in the library constructed `EventDataSetWriter`, and it was not an `IDataSetWriter`; - `WriterGroup` appends at most one message per writer per cycle, whereas an event writer produces one per occurrence. Now: `EventPublishedDataSet` is an `IPublishedDataSet` whose general `SampleAsync` drains one occurrence per cycle declared as an event; `EventDataSetWriter` is an `IDataSetWriter`; `PubSubApplication` builds an event dataset when the configured `DataSetSource` is a `PublishedEventsDataType` and the registered source is an `IEventSampler`; and a writer group drains every pending occurrence in one publish cycle. Event-writer sequence numbers now use the WriterGroup checkpoint state, so failover and restart resume above the shared checkpoint. The rows-returning `EventPublishedDataSet.SampleAsync` is renamed `SampleEventsAsync`, both to make room for the interface member and to match `IEventSampler.SampleEventsAsync`. ### 3. A metadata announcement hides its own payload `JsonMetaDataMessage` documents that the payload *"is exposed both on the base `PubSubNetworkMessage.MetaData` property and on `MetaDataPayload` so callers can use whichever accessor matches their fluent style."* `MetaDataPublisher` set only `MetaDataPayload`, so the documented contract was false: any consumer, transform or encoder hook reading the base property saw an announcement as a message carrying nothing. Both are now populated. Dataset subscriptions also use a dispose-safe subscribe/recheck handshake, preventing a concurrent shutdown from leaving a late handler attached. ### 4. JSON DataValue status used the wrong member name Part 6 section 5.4.2.18 Table 42 names the `DataValue` status member `Status`; `StatusCode` is its data type. `JsonEncoder` and `JsonDecoder` instead shared the member name `StatusCode`, so stack-to-stack round-trips passed while standards-conformant peers could not exchange non-Good status values. Both directions now use `Status`. The encoder regression test also verifies that `StatusCode` is absent from the emitted `DataValue` object. Fixes #4111. ### Compatibility The snapshot property is optional and defaults to null, so existing PubSub sources and current-state sampling behavior remain unchanged. The `EventPublishedDataSet.SampleAsync` rename is source-breaking on a type that could not previously be reached from the runtime. The JSON `DataValue` wire member intentionally changes from `StatusCode` to the specification-defined `Status`. No legacy alias is retained: the encoder emits `Status`, and the decoder expects `Status`. ### Testing `Opc.Ua.PubSub.Tests` on `net10.0`: 1341 passed, 1 skipped, 0 failed. New coverage: - `WriterGroupDeclaredMessageTypeTests` — a declared type is honoured, declared samples never become delta frames and are never suppressed as unchanged, and an undeclared source keeps the existing key-frame cadence. - `EventDataSetWriterTests.EventPublishedDataSet_SamplesOneOccurrencePerSnapshotAsync` — the general contract drains one occurrence per call, declares it as an event, and reports nothing when exhausted. - `WriterGroupEventWriterHotStandbyContinuesSequenceNumberFromSharedCheckpointAsync` — event messages share the checkpointed sequence state and continue monotonically after standby promotion. Issue #4111 validation: - `Opc.Ua.Types.Tests` JSON encoder/decoder fixtures on `net10.0`: 274 passed. - `Opc.Ua.Core.Encoders.Tests` JSON conformance cases on `net10.0`: 604 passed. - `Opc.Ua.PubSub.Tests` JSON fixtures on `net10.0`: 88 passed. - Targeted `net48` regression tests: 2 passed; core JSON conformance cases: 572 passed. - Review-feedback fixtures on `net48`: 11 passed. CI-fix validation: - `Opc.Ua.Core.Tests` on `net10.0`: 4145 passed, 86 skipped. - `Opc.Ua.Core.Tests` on `net48`: 4070 passed, 92 skipped. - Patch coverage check passes after adding targeted metadata and event publishing tests. --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 1a300bc8-8bde-4a82-8fc3-476ef837bc6a Copilot-Session: 9f18bf87-795f-40a9-8494-b6e6334c4a97
OPC UA .NET Standard Stack
🆕 This is version 2.0 of the OPC UA .NET Standard Stack (current
master).Looking for the supported 1.x release? It lives on the
master378branch (last release:1.5.378). All new feature work happens here onmaster;master378continues to receive security and critical-bug fixes for the 1.x line.
The official OPC Foundation reference implementation of OPC UA for .NET — a certified, cross-platform stack with client, server, PubSub, GDS, complex types, and source-generated tooling. Used in production across industrial control, manufacturing, energy, and IoT systems.
📦 What it is
- A full-stack OPC UA implementation — Core / Client / Server / PubSub / GDS / LDS / Complex Types / Device Integration libraries built on .NET, with UA-TCP and HTTPS transports.
- Cross-platform — runs on .NET 10, .NET 9, .NET 8 (LTS), .NET Framework 4.8, and .NET Standard 2.1; ships Native-AOT-friendly assemblies.
- Certified for compliance — the reference server has been certified through an OPC Foundation Certification Test Lab and is continuously verified against the latest Compliance Test Tool (CTT).
- Companion-spec coverage — Part 9 (Alarms & Conditions), Part 11 (Historical Access), Part 13 (Aggregates), Part 16 (State Machines), Part 17 (Alias Names), Part 18 (Role Management), Part 20 (File Transfer), Part 100 (Device Integration), OPC-10030 (ISA-95 Common Model) with OPC-10031-4 Job Control V1/V2, OPC 10100-1 (WoT Connectivity).
- Modern developer surface — first-class
Microsoft.Extensions.DependencyInjectionhosting (services.AddOpcUa()), fluent server + client builders, source-generated NodeManagers and DataTypes, and an MCP server so LLMs / Copilot can drive an OPC UA client.
For the full feature breakdown see OPC UA Profiles and Facets and the What's New in 2.0 tour.
🚀 Getting started
You need the .NET 10 SDK to build the repo. From the repository root:
dotnet restore UA.slnx
dotnet build UA.slnx
For the supported target frameworks and platform notes see
the Developer Guide. The official NuGet packages
are published to nuget.org under the OPCFoundation.NetStandard
prefix — the meta package
OPCFoundation.NetStandard.Opc.Ua
pulls in everything, or pick the split
OPCFoundation.NetStandard.Opc.Ua.Core / .Client / .Server /
.Bindings.Https packages directly. Preview builds for every successful
master build are available in the
Azure DevOps opcua-preview feed.
Sample applications
Each sample has its own README.md with build and run instructions.
Reference applications
- Console Reference Server — the certified reference server (with Quickstarts, CTT, and Mono configs). Also ships as a Docker container.
- Console Reference Client — cross-platform reference client demonstrating sessions, subscriptions, browsing, and method calls.
- Console LDS Server — a standalone
Local Discovery Server built on
Opc.Ua.Lds.Server.
PubSub samples
- Console Reference PubSub Client —
one executable with
publisher,subscriber, andexternal(external-server adapter) modes across the supported transport profiles.
Minimal / Device-Integration samples
- Minimal Calc Server — minimal server built on the source-generated NodeManager pipeline (Calc model).
- Minimal Boiler Server — minimal Boiler-model server with the fluent state-machine builder; Native-AOT publishable.
- Pump Device Integration Server —
minimal Device Integration (Part 100) server using
Opc.Ua.Di.Server's fluent builder. - Minimal ISA-95 Server — minimal server hosting the OPC-10030 ISA-95 Common Model together with OPC-10031-4 Job Control V1 and V2, using the typed common-model builder and the in-memory Job Control provider.
More sample projects are maintained in the companion OPC UA .NET Samples repository.
Developer tools
- OPC UA MCP Server — installable .NET tool and container that exposes OPC UA client operations as MCP tools for LLMs and Copilot.
🔧 Migrating from 1.5.378 to 2.0
The 2.0 release introduces breaking API changes, and comes with a full prescriptive migration guide that links to per-area documentation covering telemetry, packages, source generation, types, encoders, node states, identity, certificates, configuration, sessions / subscriptions, alarms / model change, and TimeProvider.
Most of the mechanical migration work is automated:
OPCFoundation.NetStandard.Opc.Ua.MigrationAnalyzerNuGet — install it in your project to get analyzer warnings (UA0001–UA0022)- one-click code fixes for the patterns in the guide. Setup steps are in the package's NugetREADME.md.
- Migration agent skill — the
opcua-v20-migrationskill walks Copilot / Claude / any coding agent through installing the NuGet, runningdotnet format analyzersto apply auto-fixes, and handling the small residual manual patterns. The skill knows which sub-doc to load for each symptom so it stays context-efficient.
If you are still on 1.x and not ready to upgrade, stay on the
master378
branch — it continues to receive security and critical-bug fixes.
🤝 Contributing and license
Community contributions are welcome. Fork the repository, make your changes on a branch, and open a pull request; see CONTRIBUTING.md for the contribution workflow.
Contributors must sign the OPC Foundation Contributor License Agreement (CLA). The CLA "I AGREE" gate is presented automatically on your first PR.
The project is licensed under the OPC Foundation MIT License. Report security vulnerabilities via the process documented in SECURITY.md.
📚 Further reading
- Documentation index — every per-feature doc with a one-line description.
- What's New in 2.0 — narrative tour of the 1.5.378 → 2.0 changes grouped by theme and layer.
- OPC UA Profiles and Facets — facets / transports / security policies the stack implements.
- Migration Guide — prescriptive
per-version migration reference (links to
docs/migrate/2.0.x/). - OPC UA Online Reference — the official OPC 10000 series specification index.
- OPC UA .NET Samples — companion repository with more sample applications.
- Preview NuGet feed — prerelease builds from Azure DevOps.