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fix: resolve System.Memory version conflict on .NET Framework (net462)#5303

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thomhurst merged 1 commit intomainfrom
fix/fsharp-nuget-tester-system-memory
Mar 30, 2026
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fix: resolve System.Memory version conflict on .NET Framework (net462)#5303
thomhurst merged 1 commit intomainfrom
fix/fsharp-nuget-tester-system-memory

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Summary

  • Add explicit System.Memory 4.6.3 package reference to NuGet tester projects (C#, F#, VB.NET) for .NET Framework targets
  • Add System.Memory to Directory.Packages.props for central package management

Root Cause

The NuGet tester projects target both .NET Framework (net462) and .NET Core. They reference TUnit.NugetTester.Library (netstandard2.0), which creates two NuGet resolution paths for System.Memory:

Path Package Assembly Version
Direct transitive (net461 lib) 4.5.5 4.0.1.2
Via Library (netstandard2.0 lib) 4.6.3 4.0.2.0

MSBuild picks 4.0.1.2 as "primary" and copies that DLL. At runtime, code compiled against 4.0.2.0 fails with FileLoadException.

Adding an explicit System.Memory 4.6.3 reference makes it the primary, resolving to assembly version 4.0.5.0 (net462 lib) which unifies both.

Test plan

  • Verified all three tester projects (C#, F#, VB.NET) build for net462 with no MSB3277 warnings
  • CI passes for modularpipeline (windows-latest) with net462 target

Fixes #5297

Add explicit System.Memory 4.6.3 package reference to NuGet tester
projects when targeting .NET Framework. The conflict arose because
transitive dependencies resolved System.Memory 4.5.5 (assembly 4.0.1.2
via net461) and 4.6.3 (assembly 4.0.2.0 via netstandard2.0) through
different paths, causing a FileLoadException at runtime.

Fixes #5297
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Code Review

Summary: This PR fixes a assembly version conflict on .NET Framework targets (net462) that caused a at runtime.

Analysis

The root cause is well-diagnosed: two transitive resolution paths produce different assembly versions ( via net461 and via netstandard2.0), causing MSBuild to pick the wrong one as "primary". The fix forces a unified resolution by pinning an explicit reference to 4.6.3.

What's Good

  • Correct use of CPM (Central Package Management): Adding to Directory.Packages.props defines the version centrally without leaking it to other projects — only projects that explicitly reference the package will get it.

  • Correct condition syntax: Using '$(TargetFrameworkIdentifier)' == '.NETFramework' is the right idiom for multi-targeted projects. It's more robust than checking $(TargetFramework) directly (which would only match exact TFM strings like net462, not net45 etc.).

  • Minimal blast radius: Changes are scoped to only the NuGet tester projects where the conflict manifests, and only for .NET Framework targets.

  • Consistent application: All three language variants (C#, F#, VB.NET) are updated identically.

Minor Observation

The alternative fix — using <BindingRedirect> in an app.config — would be more brittle and harder to maintain across three projects. The chosen approach of an explicit package reference is the correct MSBuild solution for this class of problem.

One thing worth noting: the explicit reference resolves to assembly version 4.0.5.0 (net462 lib) rather than unifying at 4.0.2.0 — this is a "superset" unification that may silently satisfy both dependency paths. If a future System.Memory version reintroduces a breaking change for net462, this conditional reference ensures only .NET Framework consumers are affected.

Verdict

Clean, targeted fix with a thorough root cause analysis. The approach is correct and the implementation is consistent. No issues found.

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Code Review

Summary: This PR fixes a System.Memory assembly version conflict on .NET Framework targets (net462) that caused a FileLoadException at runtime.

Analysis

The root cause is well-diagnosed: two transitive resolution paths produce different assembly versions (4.0.1.2 via net461 and 4.0.2.0 via netstandard2.0), causing MSBuild to pick the wrong one as "primary". The fix forces unified resolution by pinning an explicit reference to 4.6.3.

What's Good

  • Correct use of CPM (Central Package Management): Adding to Directory.Packages.props defines the version centrally without leaking it to other projects — only projects that explicitly reference the package will get it.

  • Correct condition syntax: Using '$(TargetFrameworkIdentifier)' == '.NETFramework' is the right idiom for multi-targeted projects. It's more robust than checking $(TargetFramework) directly (which would only match exact TFM strings like net462, not net45 etc.).

  • Minimal blast radius: Changes are scoped to only the NuGet tester projects where the conflict manifests, and only for .NET Framework targets.

  • Consistent application: All three language variants (C#, F#, VB.NET) are updated identically.

Minor Observation

The alternative fix — using <BindingRedirect> in an app.config — would be more brittle and harder to maintain across three projects. The chosen approach of an explicit package reference is the correct MSBuild solution for this class of problem.

Worth noting: the explicit reference resolves to assembly version 4.0.5.0 (net462 lib), which is a "superset" unification that satisfies both dependency paths. If a future System.Memory version reintroduces a breaking change for net462, the conditional reference ensures only .NET Framework consumers are affected.

Verdict

Clean, targeted fix with thorough root cause analysis. The approach is correct and the implementation is consistent. No issues found. ✓

@thomhurst thomhurst merged commit 67d0bc9 into main Mar 30, 2026
16 checks passed
@thomhurst thomhurst deleted the fix/fsharp-nuget-tester-system-memory branch March 30, 2026 11:01
This was referenced Mar 30, 2026
intellitect-bot pushed a commit to IntelliTect/EssentialCSharp.Web that referenced this pull request Apr 1, 2026
Updated [TUnit](https://github.com/thomhurst/TUnit) from 1.23.7 to
1.24.13.

<details>
<summary>Release notes</summary>

_Sourced from [TUnit's
releases](https://github.com/thomhurst/TUnit/releases)._

## 1.24.13

<!-- Release notes generated using configuration in .github/release.yml
at v1.24.13 -->

## What's Changed
### Other Changes
* perf(mocks): optimize MockEngine for lower allocation and faster
verification by @​thomhurst in
thomhurst/TUnit#5319
* Remove defunct `UseTestingPlatformProtocol` reference for vscode by
@​erwinkramer in thomhurst/TUnit#5328
* perf(aspnetcore): prevent thread pool starvation during parallel
WebApplicationTest server init by @​thomhurst in
thomhurst/TUnit#5329
* fix TUnit0073 for when type from from another assembly by @​SimonCropp
in thomhurst/TUnit#5322
* Fix implicit conversion operators bypassed in property injection casts
by @​Copilot in thomhurst/TUnit#5317
* fix(mocks): skip non-virtual 'new' methods when discovering mockable
members by @​thomhurst in thomhurst/TUnit#5330
* feat(mocks): IFoo.Mock() discovery with generic fallback and ORP
resolution by @​thomhurst in
thomhurst/TUnit#5327
### Dependencies
* chore(deps): update tunit to 1.24.0 by @​thomhurst in
thomhurst/TUnit#5315
* chore(deps): update aspire to 13.2.1 by @​thomhurst in
thomhurst/TUnit#5323
* chore(deps): update verify to 31.14.0 by @​thomhurst in
thomhurst/TUnit#5325

## New Contributors
* @​erwinkramer made their first contribution in
thomhurst/TUnit#5328

**Full Changelog**:
thomhurst/TUnit@v1.24.0...v1.24.13

## 1.24.0

<!-- Release notes generated using configuration in .github/release.yml
at v1.24.0 -->

## What's Changed
### Other Changes
* perf: optimize TUnit.Mocks hot paths by @​thomhurst in
thomhurst/TUnit#5304
* fix: resolve System.Memory version conflict on .NET Framework (net462)
by @​thomhurst in thomhurst/TUnit#5303
* fix: resolve CS0460/CS0122/CS0115 when mocking concrete classes from
external assemblies by @​thomhurst in
thomhurst/TUnit#5310
* feat(mocks): parameterless Returns() and ReturnsAsync() for async
methods by @​thomhurst in thomhurst/TUnit#5309
* Fix typo in NUnit manual migration guide by @​aa-ko in
thomhurst/TUnit#5312
* refactor(mocks): unify Mock.Of<T>() and Mock.OfPartial<T>() into
single API by @​thomhurst in
thomhurst/TUnit#5311
* refactor(mocks): clean up Mock API surface by @​thomhurst in
thomhurst/TUnit#5314
* refactor(mocks): remove generic/untyped overloads from public API by
@​thomhurst in thomhurst/TUnit#5313
### Dependencies
* chore(deps): update tunit to 1.23.7 by @​thomhurst in
thomhurst/TUnit#5305
* chore(deps): update dependency mockolate to 2.1.1 by @​thomhurst in
thomhurst/TUnit#5307

## New Contributors
* @​aa-ko made their first contribution in
thomhurst/TUnit#5312

**Full Changelog**:
thomhurst/TUnit@v1.23.7...v1.24.0

Commits viewable in [compare
view](thomhurst/TUnit@v1.23.7...v1.24.13).
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FSharp NuGet tester fails on Windows net462: System.Memory version conflict

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