Rx .NET: ToTask vs LastAsync vs RunAsync

Question

Reactive Extensions has these three methods:

ToTask: Returns a task that will receive the last value or the exception produced by the observable sequence.
LastAsync: Returns the last element of an observable sequence
RunAsync: Gets an awaiter that returns the last value of the observable sequence or throws an exception if the sequence is empty.

They sound very similar. How would I choose which one to use?

I would use `RunAsync`, because it seems to have more flexibility :) — Momoro, Oct 26 '19 at 05:41

Andrii Litvinov · Answer 1 · 2019-10-30T09:08:34.837

1

You should choose based on what you want to do with returning value, as these methods have different return types with different capabilities. If you only want to await last result you can use any of the methods above as they provide same behavior in this case. They all handle empty observable collections and exceptions when awaited.

edited Oct 30 '19 at 09:08

answered Oct 26 '19 at 09:56

Andrii Litvinov

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So where lies the difference then? – Monsignor May 26 '23 at 08:16
The difference is in the behavior of these methods and in the returning types, which can be consumed differently. – Andrii Litvinov May 26 '23 at 10:25

Rx .NET: ToTask vs LastAsync vs RunAsync

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