System.Collections.Immutable by Microsoft

<PackageReference Include="System.Collections.Immutable" Version="9.0.1" />

.NET API 259,376 bytes

 FrozenDictionary

public static class FrozenDictionary
Provides a set of initialization methods for instances of the FrozenDictionary<T, U> class.
public static FrozenDictionary<TKey, TValue> ToFrozenDictionary<TKey, TValue>(this IEnumerable<KeyValuePair<TKey, TValue>> source, IEqualityComparer<TKey> comparer = null)

Creates a FrozenDictionary<T, U> with the specified key/value pairs.

public static FrozenDictionary<TKey, TSource> ToFrozenDictionary<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer = null)

Creates a FrozenDictionary<T, U> from an IEnumerable<T> according to specified key selector function.

public static FrozenDictionary<TKey, TElement> ToFrozenDictionary<TSource, TKey, TElement>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer = null)

Creates a FrozenDictionary<T, U> from an IEnumerable<T> according to specified key selector and element selector functions.