Sync Method call Async Method with Async Methods inside

Question

For each Method i want create Sync and Async, But without duplicating the code. I f I call an Async Method with other Async Methods inside, is it a correct code?.

public void MethodA(){//1
    MethodAAsync().GetAwaiter();        
}

public void MethodA(){//2 is it a correct code
    MethodB();
    MethodC();
    ...code
    ...code
    ...code
    MethodD();
    MethodE();  
}

public async Task MethodAAsync(){
    await MethodBAsync(cancellationToken);
    await MethodCAsync(cancellationToken);
    ...code
    ...code
    ...code
    await MethodDAsync(cancellationToken);
    await MethodEAsync(cancellationToken);
}

//1 or 2

Stephen Cleary · Accepted Answer · 2020-09-01 20:54:46Z

4

Synchronous wrappers for asynchronous methods is an antipattern. First, I recommend that you only support an asynchronous API. But sometimes this isn't possible, e.g., for backwards compatibility reasons.

In that case, I recommend the boolean argument hack, which looks something like this:

public void MethodA() {
  MethodACore(sync: true).GetAwaiter().GetResult();
}

public Task MethodAAsync() {
  return MethodACore(sync: false);
}

private async Task MethodACore(bool sync) {
  if (sync) MethodB(); else await MethodBAsync(cancellationToken);
  if (sync) MethodC(); else await MethodCAsync(cancellationToken);
  ...code
  ...code
  ...code
  if (sync) MethodD(); else await MethodDAsync(cancellationToken);
  if (sync) MethodE(); else await MethodEAsync(cancellationToken);
}

answered Sep 1, 2020 at 20:54

Stephen Cleary

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4 Comments

ndogac Over a year ago

Why do we use .GetAwaiter.GetResult() instead of .Result?

Stephen Cleary Over a year ago

GetAwaiter().GetResult() avoids an AggregateException wrapper in the case where MethodACore throws an exception.

Saher Ahwal Over a year ago

I was told that calling Async method and awaiting on it to get Sync version is an antipattern and can cause deadlocks.

Stephen Cleary Over a year ago

@SaherAhwal: That is correct. However, this pattern is not blocking on asynchronous code, since the core method is guaranteed to complete synchronously.

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