With C# 8 the yield and foreach statements have been extended to offer asynchronously iterating through streams. IAsyncEnumerable, IAsyncEnumerator, and IAsyncDisposable have been added as asynchronous counterparts of the synchronous interfaces IEnumerable, IEnumerator, and IDisposable. This session demonstrates the foundation of asynchronous streams, as well how async streams can be used with SignalR, gRPC, EF Core (.NET 6), ASP.NET Core 6, and Azure Storage..

1. Async Streams
Christian Nagel
https://csharp.christiannagel.com

2. Christian Nagel
• Training
• Coaching
• Consulting
• Development
• Microsoft MVP
• www.cninnovation.com
• csharp.christiannagel.com
• @christiannagel

3. Topics
• Foundations
• Libraries

4. Foundations

5. What’s the yield
statement?
• yield return
• yield break
• Creates implementations for
IEnumerator, IEnumerable

6. yield & foreach
• yield implements IEnumerable and
IEnumerator interfaces
• foreach uses IEnumerable and
IEnumerator interfaces

7. Asynchronous
APIs
• Task, ValueTask, GetAwaiter
• Return a single result
• IAsyncEnumerable
• Return a result stream

8. IAsyncEnumerable

9. await foreach

10. Sync vs Async
Sync
• IDisposable
• IEnumerable
• IEnumerator
Async
• IAsyncDisposable
• IAsyncEnumerable
• IAsyncEnumerator

11. Libraries

12. Asynchronous
Streaming with
SignalR
• SignalR: real-time server-client
communication plus streaming
• ChannelReader / ChannelWriter
gives more control
• IAsyncEnumerable available since
.NET Core 3
• Async streaming is easier to use

13. SignalR - Server

14. SignalR - Client

15. gRPC
• Platform-independent binary communication…
• …including streaming

16. Async Streaming with gRPC - Server

17. Async Streaming with gRPC - Client

18. EF Core (.NET
6)
• Mapping relational and NoSQL databases to objects
• Stream results asynchronously with…
• GetAsyncEnumerator
• IAsyncEnumerator
• AsAsyncEnumerable
• IAsyncEnumerable

19. ASP.NET Core Controller

20. Calling API Controller

21. Azure Storage
• Iterate through a large list of blobs
• Working with the continuation
token is abstracted
• AsyncPageable implements
IAsyncEnumerable

22. Summary
• Task returns a result
• IAsyncEnumerable returns a continuous stream of results
• yield and foreach statements enhanced
• Many libraries support async streams

23. Thank
you!
• Source code:
https://github.com/christiannagel
• More information:
https://csharp.christiannagel.com