This is the assembly that surfaces immutable collections such as ImmutableArray<T> and ImmutableDictionary<TKey, TValue>.

Documentation can be found at https://learn.microsoft.com/dotnet/api/system.collections.immutable.

• We consider new features, new APIs and performance changes
• We consider PRs that target this library for new source code analyzers
• We don't accept refactoring changes due to new language features

See the Help Wanted issues.

System.Collections.Immutable is included in the shared framework and also provided as a NuGet package.