Custom IAsyncEnumerable operator implementations

[DL444]

With System.Linq.Async integrated into the core runtime for .NET 10, I wonder if there's any future possibility of enabling custom implementations for those async LINQ operators.

IAsyncEnumerables usually represent resources that are expensive to enumerate. Custom operator implementations that are business-aware enable optimizations that can potentially avoid a lot of wasteful overhead.

For example, an IAsyncEnumerable representing a paginated web API can implement a custom Skip() operator that replaces the in-box universal enumerate-and-discard implementation.

Skip() is what I'm most interested in for now. OrderBy() and many others might also benefit from customizations, but I recognize that these operators have more complex semantics (e.g. IComparer<TKey>) that are hard to generalize in practice.

I'm not sure what the scope and the API shape for this feature should be, hence a discussion instead of an API request.

[huoyaoyuan]

IEnumerable/IAsyncEnumerable can't support custom implementation at all. Operation customizing is achieved using IQueryable.

[DL444]

I know IQueryable<T>, but it doesn't support async streaming today, right? Or that what I should ask for is actually QueryableExtensions.ToAsyncEnumerable()?

[huoyaoyuan]

You need the query provider to support IAsyncEnumerable natively, or some IAsyncQueryable. Casting won't work in optimal way. EF core implements IAsyncEnumerble support of its queryables.

[DL444]

Now I see EntityFrameworkQueryableExtensions.AsAsyncEnumerable<TSource>(). Seems promising and I will do some research on that. Thanks for pointing it out!