Glad to see this Dart feature appearing in C#:

  Asynchronous Streams

Now you can "yield" Task<T> (~ Future<T> in Dart) and construct LINQ chains in an asynchronous fashion. I hope it streamlines reactive programming greatly.

[1] Dart - Asynchronous Programming: Streams https://www.dartlang.org/tutorials/language/streams

[2] .NET Futures: Asynchronous Streams https://www.infoq.com/news/2017/05/async-streams