Index · Quick recall Q&A
1 min readRapid overview
Quick recall Q&A
Q: What's the difference between IEnumerable and IAsyncEnumerable? A:
IEnumerable<T> uses synchronous iteration with yield return and foreach. IAsyncEnumerable<T> supports async operations with await foreach, allowing each MoveNextAsync() to be awaited. Use IAsyncEnumerable<T> when producing items requires I/O or async work.Q: How does yield return differ from return? A:
return exits the method completely. yield return suspends execution, preserving state, and resumes on the next iteration. The method becomes an iterator that produces values lazily.Q: When would you use Channels over IAsyncEnumerable? A: Use Channels when you need decoupled producers and consumers, multiple producers/consumers, backpressure control, or buffering. Use
IAsyncEnumerable<T> for simpler pull-based streaming without complex coordination.Q: What happens if you don't enumerate an iterator? A: Nothing executes. Iterator methods use deferred execution - code only runs when you iterate (foreach, ToList, etc.). This enables lazy evaluation and early termination.
Q: How do you handle cancellation in async iterators? A: Use
[EnumeratorCancellation] attribute on a CancellationToken parameter. The token is automatically threaded through when using WithCancellation() extension method.