Convert IEnumerable<Task<T>> to IObservable<T>

Question

I'm trying to use the Reactive Extensions (Rx) to buffer an enumeration of Tasks as they complete. Does anyone know if there is a clean built-in way of doing this? The ToObservable extension method will just make an IObservable<Task<T>> , which is not what I want, I want an IObservable<T> , that I can then use Buffer on.

Contrived example:

//Method designed to be awaitable
public static Task<int> makeInt()
{
     return Task.Run(() => 5);
}

//In practice, however, I don't want to await each individual task
//I want to await chunks of them at a time, which *should* be easy with Observable.Buffer 
public static void Main() 
{
    //Make a bunch of tasks
    IEnumerable<Task<int>> futureInts = Enumerable.Range(1, 100).Select(t => makeInt());

    //Is there a built in way to turn this into an Observable that I can then buffer?
    IObservable<int> buffered = futureInts.TasksToObservable().Buffer(15); //????

    buffered.Subscribe(ints => {
        Console.WriteLine(ints.Count()); //Should be 15
    });
}

Answer 1

You can use the fact that Task can be converted to observable using another overload of ToObservable() .

When you have a collection of (single-item) observables, you can create a single observable that contains the items as they complete using Merge() .

So, your code could look like this:

futureInts.Select(t => t.ToObservable())
          .Merge()
          .Buffer(15)
          .Subscribe(ints => Console.WriteLine(ints.Count));