How do I cancel an async List<T>.ForEach [duplicate]

Question

I have the following code:

contact.AddressList.ForEach(async (address) => { //...... returnValues = await _apiDataService.CallEndPointAPIAsync( Contact, token, "ContactApiEndpoint"); if (returnValues.Response.StatusCode != System.Net.HttpStatusCode.OK) { //jump out of here } });

If for any reason the call, doesn't return ok, I want to jump of here, I thought I'd get away with break; but that's not allowed at this point.

Convert to it to a regular "for each". By the way the code inside the foreach block is not awaited in the function it is in since contact.AddressList.ForEach is not awaited. (and can not be) — Magnus
– Magnus, Commented Sep 6, 2023 at 11:01
My advice: never use the ForEach extension, it is really pointless. It doesn't make your code more readable, it's slower since it needs to create a lambda, there are side effects such as closures, and arguably goes against Linq principles (i.e. it's not a query, you can mutate the data) — DavidG
– DavidG, Commented Sep 6, 2023 at 11:14
@DavidG: ForEach isn't a LINQ extension method, it's an own method of List<T>. Still valid comment though, and I agree. — Orion
– Orion, Commented Sep 6, 2023 at 11:25
What are you actually trying to do? Execute these requests one after the other and stop when at the first failing? Then use a standard for or foreach loop. Execute them in parallel? Then what happens to the other requests, when one fails? — derpirscher
– derpirscher, Commented Sep 6, 2023 at 12:07

YungDeiza · Accepted Answer · 2023-09-06 11:52:49Z

1

You can't.

Just use a normal foreach loop as mentioned in various comments:

foreach (var address in contact.AddressList) { ...... returnValues = await _apiDataService.CallEndPointAPIAsync(Contact, token, "ContactApiEndpoint"); if (returnValues.Response.StatusCode != System.Net.HttpStatusCode.OK) { break; } }

answered Sep 6, 2023 at 11:52

YungDeiza

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9 Comments

MakePeaceGreatAgain Over a year ago

however that will effectivly run all the tasks synchronously one after the other. We don't know if that is a problem, though.

YungDeiza Over a year ago

@MakePeaceGreatAgain So does for ForEach - It's not Parallel.ForEach

derpirscher Over a year ago

@YungDeiza but not if the Action passed into ForEach is async. In that case, it will just start each of the actions but don't await them ...

Theodor Zoulias Over a year ago

@MakePeaceGreatAgain it's sequentially, not synchronously. The tasks run sequentially one after the other.

bilpor Over a year ago

This one does it...I dont need to do it parallel as there will only be max 5 awaits and the idea is that I want to stop if any fail.

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