Async.TryCancelled<'T> (Método de F#)

Crea un cálculo asincrónico que ejecuta la función de cálculo especificada.Si se cancela este cálculo antes de que se complete, se ejecutará el cálculo generado por la ejecución de la función de compensación.

Espacio de nombres/Ruta de acceso del módulo: Microsoft.FSharp.Control

Ensamblado: FSharp.Core (en FSharp.Core.dll)

// Signature:
static member TryCancelled : Async<'T> * (OperationCanceledException -> unit) -> Async<'T>

// Usage:
Async.TryCancelled (computation, compensation)

Parámetros

• computation
  Tipo: Async<'T>

  Cálculo asincrónico de entrada.

• compensation
  Tipo: OperationCanceledException -> unit

  Función que se va a ejecutar si se cancela el cálculo.

Valor devuelto

Cálculo asincrónico que ejecuta la función de compensación si se cancela el cálculo de entrada.

Ejemplo

En el ejemplo de código siguiente se muestra cómo usar Async.TryCancelled para ejecutar un cálculo cancelable.

open System
open System.Windows.Forms

let form = new Form(Text = "Test Form", Width = 400, Height = 400)
let panel1 = new Panel(Dock = DockStyle.Fill)
panel1.DockPadding.All <- 10
let spacing = 5
let startAsyncButton = new Button(Text = "Start", Enabled = true)
let controlHeight = startAsyncButton.Height
let button2 = new Button(Text = "Start Invalid", Top = controlHeight + spacing)
let cancelAsyncButton = new Button(Text = "Cancel",
                                   Top = 2 * (controlHeight + spacing),
                                   Enabled = false)
let updown1 = new System.Windows.Forms.NumericUpDown(Top = 3 * (controlHeight + spacing), 
                                                     Value = 20m, Minimum = 0m,
                                                     Maximum = 1000000m)
let label1 = new Label (Text = "", Top = 4 * (controlHeight + spacing),
                        Width = 300, Height = 2 * controlHeight)
let progressBar = new ProgressBar(Top = 6 * (controlHeight + spacing),
                                  Width = 300)
panel1.Controls.AddRange [| startAsyncButton; button2; cancelAsyncButton;
                            updown1; label1; progressBar; |]
form.Controls.Add(panel1)

// Recursive isprime function.
let isprime number =
    let rec check count =
        count > number/2 || (number % count <> 0 && check (count + 1))
    check 2

let isprimeBigInt number =
    let rec check count =
        count > number/2I || (number % count <> 0I && check (count + 1I))
    check 2I

let computeNthPrime (number) =
     if (number < 1) then
         invalidOp <| sprintf "Invalid input for nth prime: %s." (number.ToString())
     let mutable count = 0
     let mutable num = 1I
     let isDone = false
     while (count < number) do
         num <- num + 1I
         if (num < bigint System.Int32.MaxValue) then
             while (not (isprime (int num))) do
                 num <- num + 1I
         else
             while (not (isprimeBigInt num)) do
                 num <- num + 1I
         count <- count + 1
     num

let async1 context value =
    let asyncTryWith =
        async {
                    try
                        let nthPrime = ref 0I
                        for count in 1 .. value - 1 do
                            // The cancellation check is implicit and
                            // cooperative at for!, do!, and so on.
                            nthPrime := computeNthPrime(count)
                            // Report progress as a percentage of the total task.
                            let percentComplete = (int)((float)count /
                                                        (float)value * 100.0)
                            do! Async.SwitchToContext(context)
                            progressBar.Value <- percentComplete
                            do! Async.SwitchToThreadPool()
                        // Handle the case in which the operation succeeds.
                        do! Async.SwitchToContext(context)
                        label1.Text <- sprintf "%s" ((!nthPrime).ToString())
                    with 
                        | e -> 
                            // Handle the case in which an exception is thrown.
                            do! Async.SwitchToContext(context)
                            MessageBox.Show(e.Message) |> ignore
                }
    async {
        try
            do! Async.TryCancelled(asyncTryWith,
                                   (fun oce -> 
                                      // Handle the case in which the user cancels the operation.
                                      context.Post((fun _ ->
                                          label1.Text <- "Canceled"), null)))
        finally 
            context.Post((fun _ ->
                updown1.Enabled <- true
                startAsyncButton.Enabled <- true
                cancelAsyncButton.Enabled <- false),
                null)
    }

startAsyncButton.Click.Add(fun args -> 
    cancelAsyncButton.Enabled <- true
    let context = System.Threading.SynchronizationContext.Current
    Async.Start(async1 context (int updown1.Value)))
button2.Click.Add(fun args ->
   let context = System.Threading.SynchronizationContext.Current
   Async.Start(async1 context (int (-updown1.Value))))
cancelAsyncButton.Click.Add(fun args -> Async.CancelDefaultToken())
Application.Run(form)

Plataformas

Windows 8, Windows 7, Windows Server 2012, Windows Server 2008 R2

Información de versiones

Versiones de la biblioteca básica de F#

Se admite en: 2.0, 4.0, portables

Vea también

Referencia

Control.Async (Clase de F#)

Microsoft.FSharp.Control (Espacio de nombres de F#)