Unexpected Behavior with C# 10 Async Streams and CancellationToken in Real-Time Data Processing
I'm trying to debug I'm upgrading from an older version and I'm confused about I'm working on a real-time data processing application using C# 10 and async streams..... The goal is to continuously fetch data from an external API and process it as it arrives. I've implemented an `IAsyncEnumerable<T>` to handle streaming data, but I'm encountering an unexpected issue when trying to cancel the operation using a `CancellationToken`. The cancellation seems to not take effect until the current item has been processed, which I expected, but in some cases, it seems to not cancel at all. Here's a simplified version of what I have: ```csharp public async IAsyncEnumerable<DataItem> FetchDataAsync(CancellationToken cancellationToken) { while (true) { cancellationToken.ThrowIfCancellationRequested(); var dataItem = await GetDataFromApiAsync(); // Fetch data from API yield return dataItem; } } public async Task ProcessDataAsync(CancellationToken cancellationToken) { await foreach (var item in FetchDataAsync(cancellationToken)) { // Simulate processing time with random delay await Task.Delay(500, cancellationToken); Console.WriteLine(item); } } ``` When I call `ProcessDataAsync(cancellationToken)` and later cancel the token, I find that the method sometimes continues processing for a few more iterations before stopping. I also receive an `OperationCanceledException`, but not consistently. I need to ensure that when a cancellation request is made, it stops fetching and processing immediately. I've tried logging the cancellation token's state, and it seems to be set correctly when I call `Cancel()`, but the loop continues processing. Any insights on how I can properly manage cancellation in this scenario or if there's a better approach to handle real-time streams while respecting cancellation tokens? My development environment is Ubuntu. I'd really appreciate any guidance on this. I'm working on a mobile app that needs to handle this. I'd love to hear your thoughts on this. This issue appeared after updating to C# stable. I appreciate any insights!