Async.SwitchToContext 方法 (F#)
建立非同步計算，此計算會在同步內容物件使用 Post方法執行接續。
命名空間/模組路徑：Microsoft.FSharp.Control
組件：FSharp.Core (在 FSharp.Core.dll 中)
// Signature:
static member SwitchToContext : SynchronizationContext -> Async<unit>
// Usage:
Async.SwitchToContext (syncContext)
參數
syncContext
型別：SynchronizationContext接受已發佈計算的同步處理內容。
傳回值
使用 syncContext 內容來執行的非同步計算。
備註
如果 syncContext 為 Null，則非同步計算等於 Async.SwitchToThreadPool。
範例
下列程式碼範例說明如何使用 Async.SwitchToContext 切換到 UI 執行緒以更新使用者介面。 在此狀況中，會更新指出計算玩成狀態的進度列。
open System.Windows.Forms
let form = new Form(Text = "Test Form", Width = 400, Height = 400)
let syncContext = System.Threading.SynchronizationContext()
let button1 = new Button(Text = "Start")
let label1 = new Label(Text = "", Height = 200, Width = 200,
Top = button1.Height + 10)
form.Controls.AddRange([| button1; label1 |] )
let async1(syncContext, form : System.Windows.Forms.Form) =
async {
let label1 = form.Controls.[1]
// Do something.
do! Async.Sleep(10000)
let threadName = System.Threading.Thread.CurrentThread.Name
let threadNumber = System.Threading.Thread.CurrentThread.ManagedThreadId
label1.Text <- label1.Text + sprintf "Something [%s] [%d]" threadName threadNumber
// Switch to the UI thread and update the UI.
do! Async.SwitchToContext(syncContext)
let threadName = System.Threading.Thread.CurrentThread.Name
let threadNumber = System.Threading.Thread.CurrentThread.ManagedThreadId
label1.Text <- label1.Text + sprintf "Here [%s] [%d]" threadName threadNumber
// Switch back to the thread pool.
do! Async.SwitchToThreadPool()
// Do something.
do! Async.Sleep(10000)
let threadName = System.Threading.Thread.CurrentThread.Name
let threadNumber = System.Threading.Thread.CurrentThread.ManagedThreadId
label1.Text <- label1.Text +
sprintf "Switched to thread pool [%s] [%d]" threadName threadNumber
}
let buttonClick(sender:obj, args) =
let button = sender :?> Button
Async.Start(async1(syncContext, button.Parent :?> Form))
let threadName = System.Threading.Thread.CurrentThread.Name
let threadNumber = System.Threading.Thread.CurrentThread.ManagedThreadId
button.Parent.Text <- sprintf "Started asynchronous workflow [%s] [%d]" threadName threadNumber
()
button1.Click.AddHandler(fun sender args -> buttonClick(sender, args))
Application.Run(form)
平台
Windows 8 中， Windows 7， Windows Server 2012 上， Windows Server 2008 R2
版本資訊
F# 核心程式庫版本
支援版本:2.0， 4.0，可攜式執行檔 (PE)。