Does a pass-through async method really need the await/async pattern? [duplicate]

Question

Let's say I have an method that calls another async method immediately or similar:

//Main method
public async Task<int> Foo1( int x )
{
     var result = await DoingSomethingAsync(x );
     return DoSomethingElse(result );
}  
//other method
public async Task<int> Foo2( Double double )
{
     return await Foo1( Convert.ToInt32(double ) );
}  

Is there any specific reason that Foo2 needs/should have async/await, as opposed to simply calling:

//other method
public Task<int> Foo3( Double double )
{
     return Foo1( Convert.ToInt32( double ) );
}  

In a consumer, this would still be awaited, likeso, regardless of:

int x = await Foo1(1);
int x = await Foo2(1D);
int x = await Foo3(1D);

All those statements will compile. Will the compiler generate different IL for the two different methods?

Answer 1

It depends. In particular, the exception behavior is different if Convert.ToInt32 throws.

I have a whole blog post on the subject, but in summary, I would use async/await here because the exception would be placed on the returned task. Otherwise, the exception would be thrown directly.

Throwing exceptions directly is only acceptable for precondition exceptions (i.e., it's a violation of the API to pass a double that can't be converted to an int). And even then (for precondition exceptions) you can choose to either throw exceptions directly or place them on the returned task.