Async.StartAsTask<'T> Method (F#)

Executes a computation in the thread pool. Returns a Task that will be completed in the corresponding state once the computation terminates (produces the result, throws exception or gets canceled) If no cancellation token is provided then the default cancellation token is used.

Namespace/Module Path: Microsoft.FSharp.Control

Assembly: FSharp.Core (in FSharp.Core.dll)

// Signature:
static member StartAsTask : Async<'T> * ?TaskCreationOptions * ?CancellationToken -> Task<'T>

// Usage:
Async.StartAsTask (computation)
Async.StartAsTask (computation, taskCreationOptions = taskCreationOptions, cancellationToken = cancellationToken)


  • computation
    Type: Async<'T>

    The computation to execute.

  • taskCreationOptions
    Type: TaskCreationOptions

    Optional task creation options.

  • cancellationToken
    Type: CancellationToken

    Optional cancellation token.

Return Value

A Task<TResult> object that represents the given computation.


The following code example demonstrates the use of Async.StartAsTask.

open System.Windows.Forms

let bufferData = Array.zeroCreate<byte> 100000000

let async1 =
     async {
       use outputFile = System.IO.File.Create("longoutput.dat")
       do! outputFile.AsyncWrite(bufferData) 

let form = new Form(Text = "Test Form")
let button = new Button(Text = "Start")
button.Click.Add(fun args -> let task = Async.StartAsTask(async1)
                             printfn "Do some other work..."
                             printfn "done")


Windows 7, Windows Vista SP2, Windows XP SP3, Windows XP x64 SP2, Windows Server 2008 R2, Windows Server 2008 SP2, Windows Server 2003 SP2

Version Information

F# Runtime

Supported in: 4.0


Not supported

See Also


Control.Async Class (F#)

Microsoft.FSharp.Control Namespace (F#)