Whole function chain needs to be marked async in C#-CodePudding

I have a existing program and I need to call a 3rd party library function that provides only async operations.

Main -> f1() - f2() -> f3() -> f4()

f4 calls an async method of 3rd party. So f4 has to be marked async, then f3 has to be marked async and all the way up to main(). Is that correct understanding or not?

CodePudding user response：

The short version is "yes".

The longer version is that you technically can do a few things to avoid that, but: you'll be fighting the language and runtime at every step; it will certainly be a lot more convenient if you simply switch to async/await in that call-path. And yes, for this reason awaitable types are effectively "infectious" - it quickly spreads to more and more if your code. However, this is usually without much (if any) harm, and often has great advantages for scalability. A very benign infection.

CodePudding user response：

Here's the situation that you're describing in your question:

async Task Main() { await F1(); }
private async Task F1() { await F2(); }
private async Task F2() { await F3(); }
private async Task F3() { await F4(); }
private async Task F4() { await ThirdParty.LibraryFunction(); }

public class ThirdParty
{
    public static Task LibraryFunction() => Task.Delay(TimeSpan.FromSeconds(1.0));
}

Do I need to await everything. No.

This works just fine:

async Task Main() { await F1(); }
private Task F1() => F2();
private Task F2() => F3();
private Task F3() => F4();
private Task F4() => ThirdParty.LibraryFunction();

public class ThirdParty
{
    public static Task LibraryFunction() => Task.Delay(TimeSpan.FromSeconds(1.0));
}

And what if F4 need to use the result of the library function? Well that's when ContinueWith comes in to play.

private Task F4() =>
    ThirdParty
        .LibraryFunction()
        .ContinueWith(t =>
        {
            Console.WriteLine("Done.");
        });

Just remember that async/await is just syntactic sugar added on to the language to support TPL.