What is the correct way to call Polly ExecuteAsync method?

Question

Executing a Policy, I've see some people call ExecuteAsync like this:

...
.ExecuteAsync(async (ct) => await GetEmployeeAsync(employeeId, ct), cancellationToken);

And like this:

...
.ExecuteAsync(ct => GetEmployeeAsync(employeeId, ct), cancellationToken);

What is the difference and which one should be used?

I don't think there is any significant difference in this 2 snippets. Just use one that you like. — vasily.sib, Mar 18 '20 at 03:35
The first generates another `IAsyncStatemachine` which is more *CIL*, and is an inefficient way of achieving no applicable difference — TheGeneral, Mar 18 '20 at 03:57
Related: [At the end of an async method, should I return or await?](https://stackoverflow.com/questions/17886992/at-the-end-of-an-async-method-should-i-return-or-await) — Theodor Zoulias, Mar 18 '20 at 20:52

score 3 · Accepted Answer · answered Mar 18 '20 at 12:01

In this simple case, there's no semantic difference. The version eliding async and await has an almost-immeasurable performance benefit.

In the general case, there are some pitfalls when eliding async and await. As a general rule, if the code does anything non-trivial, then you should keep the async and await. Only elide the async/await if the code is truly trivial - like in this case, when the delegate just binds employeeId on GetEmployeeAsync.

What is the correct way to call Polly ExecuteAsync method?

1 Answers1