C#: What is the difference between IAsyncEnumerable and IObservable?

IAsyncEnumerable — push-pull. IObservable — push.

IAsyncEnumerable:

• Pull-based.
• Consumer-controlled.
• Streaming.

IObservable:

• Push-based.
• Producer-controlled.
• Events.

1// IAsyncEnumerable
2await foreach (var item in GetItemsAsync())
3    Console.WriteLine(item);
4
5// IObservable
6source.Subscribe(x => Console.WriteLine(x));

Key: IAsyncEnumerable for streaming, IObservable for events.