# Description
This focused draft extracts the FileType handle ownership fix from
#4021. It contains only the server FileSystem handle implementation,
focused tests, and FileSystem client documentation.
## Failure
`FileHandle` issued predictable per-file identifiers without recording
the owning Session. A different Session that obtained a handle could
read, write, seek, or close the stream, and open streams survived
Session closure.
## Fix
- Generate non-zero opaque handles and bind every open stream to the
Session that called `Open`.
- Require a valid Session for `FileType.Open`, `CreateFile` when it
requests an open handle, and all subsequent handle operations.
- Reject a handle presented by another Session.
- Close only the departing Session's handles from
`FileSystemNodeManager.SessionClosingAsync`.
- Document the Session ownership and lifetime.
OPC 10000-5 Section 6.2.5.2, Table 27 states that a `fileHandle` is
valid only for the Session used to call `Open` and that the Server shall
automatically close the file when that Session closes.
## Tests
- `dotnet test tests\Opc.Ua.Server.Tests\Opc.Ua.Server.Tests.csproj -f
net10.0 --filter
"FullyQualifiedName~FileHandleTests|FullyQualifiedName~FileObjectStateTests|FullyQualifiedName~DirectoryObjectStateTests"
--no-restore`: 71 passed.
- `dotnet test tests\Opc.Ua.Server.Tests\Opc.Ua.Server.Tests.csproj -f
net48 --filter
"FullyQualifiedName~FileHandleTests|FullyQualifiedName~FileObjectStateTests|FullyQualifiedName~DirectoryObjectStateTests"
--no-restore`: 71 passed.
Both builds emitted the same existing CA1873 warnings in unchanged
`Opc.Ua.Client` files; the changed files produced no warnings.
## Related Issues
- Focused split from #4021 (closed umbrella draft); no separate issue.
## 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.
- [x] 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.
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Marc Schier