https://learn.microsoft.com/de-de/dotnet/api/system.collections.immutable.immutabledictionary-2.builder?view=dotnet-uwp-10.0&viewFallbackFrom=net-10.0
ImmutableDictionaryTKey,TValue.Builder Class (System.Collections.Immutable) | Microsoft Learn
Represents a hash map that mutates with little or no memory allocations and that can produce or build on immutable hash map instances efficiently.
class systembuildercollectionsimmutablemicrosoft