Async

Async.fs

[<AutoOpen>]
module Async

// Async extension to enable the direct use of Task<T> and Task 
// in async {} blocs

open System
open System.Threading.Tasks

type Microsoft.FSharp.Control.Async with
    static member AsyncRaise (e : #exn) =
        Async.FromContinuations(fun (_,econt,_) -> econt e)
    static member AwaitTask (t : Task) =
        let flattenExns (e : AggregateException) = e.Flatten().InnerExceptions |> Seq.nth 0
        let rewrapAsyncExn (it : Async<unit>) =
            async { try do! it with :? AggregateException as ae -> do! Async.AsyncRaise(flattenExns ae) }
        let tcs = new TaskCompletionSource<unit>(TaskCreationOptions.None)
        t.ContinueWith((fun t' ->
        if t.IsFaulted then tcs.SetException(t.Exception |> flattenExns)
        elif t.IsCanceled then tcs.SetCanceled ()
        else tcs.SetResult(())), TaskContinuationOptions.ExecuteSynchronously)
        |> ignore
        tcs.Task |> Async.AwaitTask |> rewrapAsyncExn

type Microsoft.FSharp.Control.AsyncBuilder with
    member this.Bind(t: Task<'a>, f: 'a -> Async<'b>) : Async<'b> = this.Bind(Async.AwaitTask t, f)
    member this.Bind(t: Task, f: unit -> Async<'b>) : Async<'b> = this.Bind(Async.AwaitTask t, f)