Async.RunSynchronously<'T> 方法 (F#)

更新：2010 年 7 月

執行非同步計算和正等著它的結果。

命名空間/模組路徑： Microsoft.FSharp.Control

組件：FSharp.Core (在 FSharp.Core.dll 中)

// Signature:
static member RunSynchronously : Async<'T> * ?int * ?CancellationToken -> 'T

// Usage:
Async.RunSynchronously (computation)
Async.RunSynchronously (computation, timeout = timeout, cancellationToken = cancellationToken)

參數

• computation
  型別：Async<'T>

  要執行的計算作業。

• timeout
  型別：int

  在引發 TimeoutException 之前，等待計算結果所需的時間量 (以毫秒為單位)。 如果沒有值提供的逾時，則預設值為-1 用來對應到 Infinite

• cancellationToken
  型別：CancellationToken

  要與計算產生關聯的取消語彙基元。 如果未提供一個取消語彙基元，則會使用預設的取消語彙基元。

傳回值

計算的結果。

備註

如果非同步計算作業發生例外狀況，則此函式會重新引發例外狀況。 如果未提供取消語彙基元，則會使用預設的取消語彙基元。 逾時參數是以毫秒為單位來提供。 -1 的值等於 Infinite

Async.RunSynchronously不應使用非同步程式設計的環境中的主執行緒上如在 Silverlight 架構應用程式。

範例

下列範例示範如何使用 Async.RunSynchronously執行使用所建立的非同步計算 Async.Parallel 與無逾時。

let bufferData (number:int) =
    [| for count in 1 .. 1000 -> byte (count % 256) |]
    |> Array.permute (fun index -> index)

let writeFile fileName bufferData =
    async {
      use outputFile = System.IO.File.Create(fileName)
      do! outputFile.AsyncWrite(bufferData) 
    }

Seq.init 1000 (fun num -> bufferData num)
|> Seq.mapi (fun num value -> writeFile ("file" + num.ToString() + ".dat") value)
|> Async.Parallel
|> Async.RunSynchronously
|> ignore

下列範例示範如何使用 Async.RunSynchronously與 逾時。

let bufferData (number:int) =
    [| for i in 1 .. 1000 -> byte (i % 256) |]
    |> Array.permute (fun index -> index)

// Create a counter as a reference cell that can be modified in parallel.
let counter = ref 0

// writeFileInner writes the data to an open stream
// that represents the file. It also updates the counter.

// The counter is locked because it will be accessed by
// multiple asynchronous computations.

// The counter must be updated as soon as the
// AsyncWrite completes, in the same synchronous
// program flow. There must not be a let! or do! between
// the AsyncWrite call and the counter update.
let writeFileInner (stream:System.IO.Stream) data =
    let result = stream.AsyncWrite(data)
    lock counter (fun () -> counter := !counter + 1)
    result

// writeFile encapsulates the asynchronous write operation.
// The do! includes both the file I/O operation and the
// counter update in order to keep those operations
// together.
let writeFile fileName bufferData =
    async {
      use outputFile = System.IO.File.Create(fileName)
      do! writeFileInner outputFile bufferData
      // Updating the counter here would not be effective.
    }

let async1 = Seq.init 1000 (fun num -> bufferData num)
             |> Seq.mapi (fun num value ->
                 writeFile ("file" + num.ToString() + ".dat") value)
             |> Async.Parallel
try
    Async.RunSynchronously(async1, 100) |> ignore
with
   | exc -> printfn "%s" exc.Message
            printfn "%d write operations completed successfully." !counter

範例輸出

平台

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

版本資訊

F# 執行階段

支援版本：2.0、4.0

Silverlight

支援版本：3

請參閱

參考

Control.Async 類別 (F#)

Microsoft.FSharp.Control 命名空間 (F#)

變更記錄

日期	History	原因
2010 年 7 月	加入程式碼範例。	資訊加強。