CODEWITHSUNDEEP
c#asynchronousasync-await
Saar Froind
Saar Froind

Reputation: 11

Is it possible to await for an async-enumerable in a foreach loop?

I need to write a method that returns an IEnumerable of objects in an async-fashion and a Foreach loop that goes through the returned IEnumerable of objects from that method. I'm using .Net Core 2 and not quite sure how to approach this task. Is it possible in .netcore2 to return an async IEnumerable?

public async IEnumerable<int> MethodThatReturnsObjectsAsync()
{
}

foreach(int item in await MethodThatReturnsObjectsAsync())
{
    Action(item);
}

Thanks in advance.

Upvotes: 0

Views: 788

Answers (2)

Christian Sauer
Christian Sauer

Reputation: 10889

No, unfortunately it is not possible at the moment. .NET Core 3.0 will ship with an IAsyncEnumerable which can do that, but that's a preview for now.

Upvotes: 0

TheGeneral
TheGeneral

Reputation: 81493

Yes its fine, it only gets called once. It only creates one state machine (If your calling method is an async method.. i.e async Task, async Task<T>, Async void)

In your case

public async Task<IEnumerable<int>> Test(Action<something> action)
{
   foreach (int item in await MethodThatReturnsObjectsAsync())
   {
      action(item);
   }

   ...

   return ...
}
private static async Task<IEnumerable<int>> MethodThatReturnsObjectsAsync()
{
   throw new NotImplementedException();
}

Upvotes: 1

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