> why not

Because ContinueWith is considered antiquated in modern C# and shouldn't be used for a multitude of reasons? https://medium.com/@joni2nja/why-you-should-not-use-continue...

So does C# not have map yet?

(I figured `ContinueWith` was just dumb naming to avoid 'map' at all costs, just like how Java went with `thenApply`.)

Sure, you can use it like that, but it's not considered good practice. I think the context missing here is that most modern C# applications are going to be async all of the way down. The entry point can be async. Background service abstractions are async. Your API endpoints in ASP.NET Core are typically async as you're going to be calling some async I/O anyways (database queries, HTTP clients). There's no benefit to writing something in the old callback model when the rest of your code is async/await anyways.

> So does C# not have map yet?

Have you heard the word of our lord and savior, LINQ?

Of course.

In the article linked above: > ContinueWith allocates more than using async await

Does LINQ not carry a similar overhead?

You said, "So does C# not have map yet?", knowing full well that it did, and are now moving the goalposts.

I'll rephrase.

Does LINQ's map come with a plethora of problems like I'm told Task's map does above?

Should you avoid mapping because 'it's the old callback model' which doesn't belong in modern code?

Is map fit for purpose, or has it been disavowed?

Mapping (spelt "Select" quite often in LINQ) is entirely normal and promoted going forwards. It can optimize extremely well for simple cases. By default it is not parallel and compiles to an underlying for loop.

Or you can use it with Tasks. https://itnext.io/fun-csharp-doing-linq-to-tasks-because-tas...

(caution: contains the M word)

More from Microsoft: https://devblogs.microsoft.com/pfxteam/tasks-monads-and-linq... ; referencing Lippert https://ericlippert.com/category/monads/

ContinueWith is not a broken "map". What people usually want is Select. https://learn.microsoft.com/en-us/dotnet/csharp/linq/standar...

They're referring to not using .Wait()/.Result on awaitable functions, not about making every function async regardless of whether it needs it. This was a common pitfall that people would do back in the day to avoid having to refactor everything when adding async support to the code, since one await deep in the code could cause half your functions to need async added in a refractor.

> not about making every function async regardless of whether it needs it.

That's what you and I wrote. That's not what the article wrote.

"efforts to be async amount to nothing unless the entire call stack is async"

The entire call stack?

"it is best to go all in, and make everything async at once."

Go all in?

This beyond 'a little bit unclear' into 'incorrect' territory, especially since the preceding paragraph said "there's been lots of confusion on the best practices for async and how to use it properly."

Is there a single NB or asterisk-like comment on the whole page that walks back the "all in" comment to something like "calling sync from async is fine." ?

He explains the same thing I did right in his example. Don't use .Result to force sync over async.

He says not to blocking-wait for async methods, which is correct.

He makes no direct comment, afaik, on calling sync methods from async methods. The reader is left only with

  efforts to be async amount to nothing unless the entire call stack is async

and

  it is best to go all in, and make everything async at once.

and must somehow parse this as some of the call stack, and make some things async.

If I made mistakes feel free to file an issue or even send me a PR. It's open source! That said, you're right that I don't say how best to call sync from async methods (the latter is more difficult as there's no good way do it well).