Async.StartImmediate Method (F#)
Runs an asynchronous computation, starting immediately on the current operating system thread.
Namespace/Module Path: Microsoft.FSharp.Control
Assembly: FSharp.Core (in FSharp.Core.dll)
// Signature:
static member StartImmediate : Async<unit> * CancellationToken option -> unit
// Usage:
Async.StartImmediate (computation)
Async.StartImmediate (computation, cancellationToken = cancellationToken)
Parameters
-
The asynchronous computation to execute.
cancellationToken
Type: CancellationTokenThe optional cancellation token to associate with the computation. The default is used if this parameter is not provided.
Remarks
If no cancellation token is provided then the default cancellation token is used.
Example
The following code example shows how to use Async.StartImmediate to start an asynchronous computation on the current thread. Often, an asynchronous operation needs to update UI, which should always be done on the UI thread. When your asynchronous operation needs to begin by updating UI, Async.StartImmediate is a better choice than Async.Start, which starts the asynchronous operation on a thread pool thread.
open System.Windows.Forms
let bufferData = Array.zeroCreate<byte> 100000000
let async1 (button : Button) =
async {
button.Text <- "Busy"
button.Enabled <- false
let context = System.Threading.SynchronizationContext.Current
do! Async.SwitchToThreadPool()
use outputFile = System.IO.File.Create("longoutput.dat")
do! outputFile.AsyncWrite(bufferData)
do! Async.SwitchToContext(context)
button.Text <- "Start"
button.Enabled <- true
}
let form = new Form(Text = "Test Form")
let button = new Button(Text = "Start")
form.Controls.Add(button)
button.Click.Add(fun args -> Async.StartImmediate(async1 button))
Application.Run(form)
Platforms
Windows 8, Windows 7, Windows Server 2012, Windows Server 2008 R2
Version Information
F# Core Library Versions
Supported in: 2.0, 4.0, Portable