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A library can't directly use APIs absent from its compilation target. FSharp.Core 11 adds a net10.0 build alongside netstandard2.0 and netstandard2.1 so it can use modern .NET APIs without dropping older targets.
Target-specific APIs and behavior
The builds can expose different APIs and implementations. The targeting decision selects the modern target explicitly; it doesn't automatically follow the compiler's development target.
Which build your project uses
NuGet selects the nearest compatible asset for each project target. .NET 10 and later projects can select lib/net10.0/FSharp.Core.dll; older compatible targets select a .NET Standard asset.
To diagnose availability:
- Check the resolved FSharp.Core package version.
- Inspect the selected compile and runtime assets in
obj/project.assets.json. - Check the runtime that executes the application, not only its reference assemblies.
<LangVersion>preview</LangVersion> enables compiler behavior. It doesn't add missing Core members, select a different package asset, or provide runtime support.
Examples of the differences
| Area | Availability in Core 11 |
|---|---|
| ValueTask helpers and related overloads | Available in netstandard2.1 and net10.0, not netstandard2.0. |
Bounds-preserving Array2D.map, mapi, and copy |
The net10.0 build uses a newer .NET allocation API; .NET Standard builds retain their fallback. |
| Runtime-async return intrinsics | Exposed by the net10.0 build; compiler, language, reference, and runtime requirements also apply. |
For details, see Async and task functions and Array2D and Native AOT. Ordinary Async/Task helpers and print/printn are available across all three builds.
F# Interactive and asynchronous disposal
F# task expressions already support IAsyncDisposable resources in compatible compiled projects. The F# 11 packaging fix supplies the modern Core build to F# Interactive so equivalent use and use! code also works there. Update the toolset, not only an application's package reference.
Runtime async is a separate runtime contract
The Core build's net10.0 target doesn't establish runtime-async support. Follow the separate compiler, reference, and runtime requirements in Runtime async experiments.
See also
Collaborate with us on GitHub
The source for this content can be found on GitHub, where you can also create and review issues and pull requests. For more information, see our contributor guide.
