Files
romanett 9b034f8291 Enable nullable reference types centrally; migrate all unset and annotations-only projects (#4700)
# Description

Nullable reference types are now enabled once, in `common.props`, and
every project in the repository builds warning-clean with them.

**Configuration**
- `<Nullable>enable</Nullable>` lives in `common.props`. All per-project
`<Nullable>` settings are removed: 178 project files (enable,
annotations, and the `disable` in the three Aot test projects).
- 419 per-file `#nullable enable`/`restore` directives and the 4
`#nullable disable` directives are removed.
- Kept on purpose:
- The 5 `<auto-generated>` schema files (`UANodeSet.cs`, `UA Type
Dictionary.cs`, `OPCBinarySchema.cs`, `SecuredApplication.cs`,
`PInvokeHelper.cs`) keep `#nullable enable`. The compiler ignores the
project setting in generated code, so the directive is required there.
- `tests/Opc.Ua.Interop.LegacyPeer` keeps `disable`. It builds against
the 1.5.378 packages and does not import the repository props.
- `docs/DeveloperGuide.md` and `.github/copilot-instructions.md` now
describe the central setting.

**Migration** (the 43 unset and 13 annotations-only projects, roughly
10k diagnostics)
- **Production code: annotated at the declarations.** Covers
`tools/Opc.Ua.SourceGeneration.Core`, `src/Opc.Ua.Lds.Server` and the
LDS sample.
- Members, parameters and returns are nullable where null actually
flows.
- Null-check helpers carry `[NotNullWhen]` (`IsNull`, `IsValidXmlName`,
`IsMethodTypeDesign`).
- `CoreUtils.Format`, `Utils.Format`, `ITemplateWriter.WriteLine` take
`params object?[]`. `Template.AddReplacement` takes `string?` (rendering
already skips null replacements).
- `IRegisteredServerStore.RegisterAsync` returns
`Task<RegistrationEntry?>`: it returns null when a registration is
removed.
- Dereferences backed by an invariant (for example, the validated model)
use `!`, so runtime behaviour is unchanged.
- **Behavioural changes in production code** (small, deliberate):
- `NodeSetToModelDesign` throws `InvalidOperationException` when the
file is not a NodeSet. Before, it threw a NullReferenceException on the
next line.
- `ModelDesignValidator` starts its lookup tables empty instead of null.
A redundant `if (m_nodes == null) return;` guard is gone.
- **Test code: minimal annotations.**
  - `?` on values that can be null, `!` where the test asserts non-null.
  - `= null!` for fixture members assigned in SetUp.
- `TryGetStructure<T>(out T? x)` where the inferred `T?` broke the
`IEncodeable` constraint.
- A few redundant `== null` checks on structs (`NodeId`, `ArrayOf<T>`)
folded into the adjacent `IsNull`/`Count` checks.

**Notes for reviewers**
- The diff is large (~1,500 files) but almost entirely mechanical: `?`,
`!` and directive removal. The non-annotation changes are listed above.
- Known follow-up, not done here:
`IModelDesign.Namespaces/TargetNamespace/NamespaceUris` stay
non-nullable even though the validator returns null before it loads a
dictionary. Making them nullable would ripple through every generator
call site.

## Related Issues

- Fixes #4439

## Checklist

- [ ] I have signed the
[CLA](https://opcfoundation.org/license/cla/ContributorLicenseAgreementv1.0.pdf)
and read the
[CONTRIBUTING](https://github.com/OPCFoundation/UA-.NETStandard/blob/master/CONTRIBUTING.md)
doc.
- [ ] I have added tests that prove my fix is effective or that my
feature works and increased code coverage.
- [x] I have added all necessary documentation.
- [x] I have verified that my changes do not introduce (new) build or
analyzer warnings.
- [ ] I ran **all** tests locally using the **UA.slnx** solution against
at least .net **framework** and .net **10**, and all passed.
- [ ] I fixed **all** failing and flaky tests in the CI pipelines and
**all** CodeQL warnings.
- [ ] I have addressed **all** PR feedback received.

The "no new warnings" box covers net10.0 and net48: full non-incremental
builds of `UA.slnx`, `tools/SourceGeneration.slnx`,
`tools/MigrationAnalyzer.slnx` and the Aot test projects finished with 0
warnings and 0 errors under the repository's warnings-as-errors
settings. net9.0 and net8.0 also had no nullable diagnostics, but they
were not rebuilt after the final fixes. Tests have not been run locally
yet.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-08 08:48:13 +02:00
..

OPC 10000-110 Asset Management Basics samples

Two console applications that show the Opc.Ua.AMB* libraries end to end: a server that makes Device Integration devices and a Machinery machine manageable assets, and a client that finds and reads them with AmbClient.

Sample What it does
AmbServer Serves a cooling pump, the flow sensor it relies on and a hydraulic press as assets, and simulates their health alarms and maintenance
AmbClient Discovers every asset, prints a snapshot of each, the location hierarchies, adds and removes a documentation link, and streams health alarms and maintenance activities

The Asset Management Basics developer guide explains every API used here.

Run

In two terminals:

dotnet run --project samples/AMB/AmbServer -- --port 62553
dotnet run --project samples/AMB/AmbClient -- --insecure --seconds 60

--insecure makes the client accept the server's self-signed certificate; never use it in production. The client also takes --url <endpoint> (default opc.tcp://localhost:62553/AmbServer), --seconds <n> (how long to stream, 0 to skip) and --asset-id <id> (writes a new AssetId to the first asset that has one and finds the asset by it).

The server keeps what clients write - AssetIds, edited and added documentation links, the writable location and local time - below the local application data folder (OPC Foundation/AmbServer/state), or in the folder given with --state <directory>. Stop the server, start it again, and the client reads the values it wrote before.

What the server shows

File Shows
Program.cs AddMachinery() as the owner of the Device Integration address space, AddAssetManagement(...) with UseFileSystemStores, ConfigureAssetManagement(...) defining the location hierarchies and the ECLASS dictionary entry, ConfigureMachinery<T>() and ConfigureDevicesFor<MachineryNodeManager>(...)
Plant.cs Two DI devices registered with RegisterAsAssetAsync: every building block - configurable AssetId, DeviceHealth derived from the alarms, health alarms, maintenance activities with details, documentation links (fixed, editable, user links), version information, locations and local time, classification, requirements and capabilities, and a 0:Utilizes relation between the assets
PressConfigurator.cs A Machinery machine registered through IMachineHandle<T>.AsNode(); its servicing switches the machine into the Maintenance operation mode while it executes
PlantSimulation.cs A BackgroundService that raises and clears a bearing temperature alarm with the sensor as root cause once a minute, fails the self test of the sensor every five minutes (AssetRootCauses.Self), and moves a maintenance activity of the pump and of the press on every two minutes

Health alarms and maintenance activities are created while the owning node manager builds its address space, which is why Plant and PressConfigurator register the assets from the DI and Machinery setup.

What the client shows

Code in Program.cs Shows
connection.Session.AssetManagement(telemetry) Creating the client; registers the AMB structured types
amb.IsSupported Detecting whether the server publishes the AMB namespace
DiscoverAssetsAsync All assets from the AMB alias categories
ReadAssetAsync → AssetSnapshot Identification, DeviceHealth, alarms, maintenance, links, locations and classification in one pass
BrowseLocationsAsync The hierarchical and operational location trees and the assets in them
AddDocumentationLinkAsync, ReadDocumentationLinksAsync, RemoveDocumentationLinkAsync The DocumentationLinks AddIn
WriteAssetIdAsync, FindAssetsAsync Configuring an AssetId and finding the asset by it
ObserveHealthAlarmsAsync, AcknowledgeAsync Health alarms with severity, fault category and root causes; a cleared alarm is acknowledged
ObserveMaintenanceAsync Maintenance activities moving through Planned, Executing and Finished

SampleSession.cs is the session setup. It keeps the ApplicationInstance alive until the session closes, because the instance owns the CertificateManager the session validates with, and it creates a ManagedSession, whose default streaming subscription the observe calls use.

Troubleshooting

Symptom Fix
Client reports BadCertificateUntrusted Pass --insecure for the demo, or trust the server certificate in the client's PKI (under the local application data folder, OPC Foundation/AmbClient/pki)
AddLink / RemoveLink: refused: BadUserAccessDenied The server refuses anonymous link editing unless AuthorizeLinkEdit allows it; the sample server allows it
The stream shows nothing for a while The alarm becomes active 20 s into every minute and maintenance moves on every two minutes; stream longer with --seconds
Port already in use Start the server with --port <n> and the client with --url opc.tcp://localhost:<n>/AmbServer