libraries.md

.NET Libraries in .NET 11 Preview 2 - Release Notes

.NET 11 Preview 2 includes new .NET Libraries features & enhancements:

• Generic GetTypeInfo for System.Text.Json
• Tar archive format selection
• Matrix4x4.GetDeterminant ~15% faster

.NET Libraries updates in .NET 11:

• What's new in .NET 11 documentation

Generic GetTypeInfo for System.Text.Json

A common pattern when working with System.Text.Json type metadata is to retrieve a JsonTypeInfo<T> from JsonSerializerOptions, which previously required a manual downcast from the non-generic GetTypeInfo(Type) method (dotnet/runtime#118468). New generic GetTypeInfo<T>() and TryGetTypeInfo<T>() methods on JsonSerializerOptions eliminate this cast and return strongly-typed metadata directly (dotnet/runtime#123940).

// Before: manual downcast required
JsonTypeInfo<MyType> info = (JsonTypeInfo<MyType>)options.GetTypeInfo(typeof(MyType));

// After: generic method returns the right type directly
JsonTypeInfo<MyType> info = options.GetTypeInfo<MyType>();

// TryGetTypeInfo variant for cases where the type may not be registered
if (options.TryGetTypeInfo<MyType>(out JsonTypeInfo<MyType>? typeInfo))
{
    // Use typeInfo
}

This is particularly useful when working with source generation, NativeAOT, and polymorphic serialization scenarios where type metadata access is common.

Tar Archive Format Selection

New overloads on TarFile.CreateFromDirectory accept a TarEntryFormat parameter, giving you direct control over the archive format (dotnet/runtime#123407). Previously, CreateFromDirectory always produced Pax archives. The new overloads support all four tar formats — Pax, Ustar, GNU, and V7 — for compatibility with specific tools and environments (dotnet/runtime#121819).

// Create a GNU format tar archive for Linux compatibility
TarFile.CreateFromDirectory("/source/dir", "/dest/archive.tar",
    includeBaseDirectory: true, TarEntryFormat.Gnu);

// Create a Ustar format archive for broader compatibility
TarFile.CreateFromDirectory("/source/dir", outputStream,
    includeBaseDirectory: false, TarEntryFormat.Ustar);

// Async version
await TarFile.CreateFromDirectoryAsync("/source/dir", "/dest/archive.tar",
    includeBaseDirectory: true, TarEntryFormat.Pax, cancellationToken);

Thank you @kasperk81 for this contribution!

Matrix4x4.GetDeterminant ~15% Faster

Matrix4x4.GetDeterminant now uses an SSE-vectorized implementation, improving performance by approximately 15% (dotnet/runtime#123954).

Scenario	Before	After	Improvement
GetDeterminantBenchmark	3.487 ns	2.971 ns	~15% faster

Thank you @alexcovington for this contribution!

Bug fixes

This release includes bug fixes and quality improvements across several areas:

• System.Collections
  • Fixed integer overflow in ImmutableArray range validation (dotnet/runtime#124042)
• System.IO.Compression
  • Fixed ZipArchiveEntry.ExtractToFile preserving files on extraction failure with overwrite: true (dotnet/runtime#123991)
• System.Linq
  • Fixed Append/Prepend GetCount overflow to correctly throw OverflowException (dotnet/runtime#123821)
• System.Net.Http
  • Fixed authenticated proxy credential handling for proxies that require proactive Proxy-Authorization headers (dotnet/runtime#123328, reported by @ptarjan)
  • Fixed edge-case non-ASCII host handling in HTTP logic (dotnet/runtime#123934)
• System.Numerics
  • Fixed Vector2/Vector3 EqualsAny and related methods returning incorrect results due to hidden padding elements (dotnet/runtime#123594, dotnet/runtime#123586)
  • Fixed missing early returns in TensorPrimitives.Round causing double-rounding (dotnet/runtime#124280)
• System.Reflection
  • Fixed MetadataLoadContext returning internal array types instead of Type[] from several methods (dotnet/runtime#124251, reported by @smdn)
• System.Runtime
  • Fixed vectorization of Ascii.Equals for input lengths 8–15 (dotnet/runtime#123115)

Community contributors

Thank you contributors! ❤️

• @alexcovington
• @am11
• @kasperk81
• @pentp
• @ptarjan