CODEWITHSUNDEEP
c#.netasynchronousparallel-processing
Linc Abela
Linc Abela

Reputation: 815

Async with only one await

Does this code make sense?

async Task DoSomething() {
     await service.doSomething();
}

Is it just similar in this?

Task DoSomething() {
    return service.doSomething();
}

OR is it just the same to this?

 void DoSomething() {
    service.doSomething().Wait();
}

Which code is the best on this scenario?

Upvotes: 2

Views: 354

Answers (1)

Kirk Woll
Kirk Woll

Reputation: 77546

Your initial example:

async Task DoSomething() 
{
     await service.doSomething();
}

Is a slightly more inefficient version than your first alternative:

Task DoSomething() 
{
    return service.doSomething();
}

It's more expensive because it has to create the whole state machine related to async code whereas the version shown above does not require that. If you were to use a disassembler such as IlSpy and inspect the compiler generated symbols, you'd see that a special class gets created for your async version (DoSomething<d__0> or some such) that would not be created if you did not use async.

On the other hand, your second example -- using .Wait() -- should be avoided whenever possible. It illustrates two problems:

  • Using .Wait means you're opting-out of async, which defeats the whole point. (The "async" code now gets invoked on the calling thread and blocks)
  • Using .Wait also often leads to thread deadlocks that are best solved by allowing await semantics to propagate through your code.

Upvotes: 4

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