Holds static members for creating and manipulating asynchronous computations.
See also F# Language Guide - Async Workflows.
Static member | Description |
Full Usage:
Async.RunSynchronously(computation, ?timeout, ?cancellationToken)
Parameters:
Async<'T>
-
The computation to run.
?timeout : int
-
The amount of time in milliseconds to wait for the result of the
computation before raising a TimeoutException. If no value is provided
for timeout then a default of -1 is used to correspond to Timeout.Infinite.
?cancellationToken : CancellationToken
-
The cancellation token to be associated with the computation.
If one is not supplied, the default cancellation token is used.
Returns: 'T
The result of the computation.
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If an exception occurs in the asynchronous computation then an exception is re-raised by this
function.
If no cancellation token is provided then the default cancellation token is used.
The computation is started on the current thread if SynchronizationContext.Current is null,
Thread.CurrentThread has Thread.IsThreadPoolThread
of
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Full Usage:
Async.Start(computation, ?cancellationToken)
Parameters:
Async<unit>
-
The computation to run asynchronously.
?cancellationToken : CancellationToken
-
The cancellation token to be associated with the computation.
If one is not supplied, the default cancellation token is used.
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If no cancellation token is provided then the default cancellation token is used.
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Full Usage:
Async.StartAsTask(computation, ?taskCreationOptions, ?cancellationToken)
Parameters:
Async<'T>
?taskCreationOptions : TaskCreationOptions
?cancellationToken : CancellationToken
Returns: Task<'T>
A Task that will be completed
in the corresponding state once the computation terminates (produces the result, throws exception or gets canceled)
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If no cancellation token is provided then the default cancellation token is used.
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Full Usage:
Async.StartChildAsTask(computation, ?taskCreationOptions)
Parameters:
Async<'T>
?taskCreationOptions : TaskCreationOptions
Returns: Async<Task<'T>>
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Full Usage:
Async.StartImmediate(computation, ?cancellationToken)
Parameters:
Async<unit>
-
The asynchronous computation to execute.
?cancellationToken : CancellationToken
-
The CancellationToken to associate with the computation.
The default is used if this parameter is not provided.
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If no cancellation token is provided then the default cancellation token is used.
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Full Usage:
Async.StartImmediateAsTask(computation, ?cancellationToken)
Parameters:
Async<'T>
-
The asynchronous computation to execute.
?cancellationToken : CancellationToken
-
The CancellationToken to associate with the computation.
The default is used if this parameter is not provided.
Returns: Task<'T>
A Task that will be completed
in the corresponding state once the computation terminates (produces the result, throws exception or gets canceled)
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![]() ![]() ![]() ![]() ![]() ![]() Runs an asynchronous computation, starting immediately on the current operating system thread, but also returns the execution as Task If no cancellation token is provided then the default cancellation token is used. You may prefer using this method if you want to achive a similar behviour to async await in C# as async computation starts on the current thread with an ability to return a result.
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Full Usage:
Async.StartWithContinuations(computation, continuation, exceptionContinuation, cancellationContinuation, ?cancellationToken)
Parameters:
Async<'T>
-
The asynchronous computation to execute.
continuation : 'T -> unit
-
The function called on success.
exceptionContinuation : exn -> unit
-
The function called on exception.
cancellationContinuation : OperationCanceledException -> unit
-
The function called on cancellation.
?cancellationToken : CancellationToken
-
The CancellationToken to associate with the computation.
The default is used if this parameter is not provided.
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![]() ![]() ![]() ![]() ![]() ![]() Runs an asynchronous computation, starting immediately on the current operating system thread. Call one of the three continuations when the operation completes. If no cancellation token is provided then the default cancellation token is used.
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Static member | Description |
![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation that executes all given asynchronous computations in parallel, returning the result of the first succeeding computation (one whose result is 'Some x'). If all child computations complete with None, the parent computation also returns None. If any child computation raises an exception, then the overall computation will trigger an exception, and cancel the others. The overall computation will respond to cancellation while executing the child computations. If cancelled, the computation will cancel any remaining child computations but will still wait for the other child computations to complete. |
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Full Usage:
Async.FromContinuations(callback)
Parameters:
('T -> unit) * (exn -> unit) * (OperationCanceledException -> unit) -> unit
-
The function that accepts the current success, exception, and cancellation
continuations.
Returns: Async<'T>
An asynchronous computation that provides the callback with the current continuations.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation that captures the current success, exception and cancellation continuations. The callback must eventually call exactly one of the given continuations.
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Full Usage:
Async.Parallel(computations, ?maxDegreeOfParallelism)
Parameters:
seq<Async<'T>>
-
A sequence of distinct computations to be parallelized.
?maxDegreeOfParallelism : int
-
The maximum degree of parallelism in the parallel execution.
Returns: Async<'T[]>
A computation that returns an array of values from the sequence of input computations.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation that executes all the given asynchronous computations, initially queueing each as work items and using a fork/join pattern. If all child computations succeed, an array of results is passed to the success continuation. If any child computation raises an exception, then the overall computation will trigger an exception, and cancel the others. The overall computation will respond to cancellation while executing the child computations. If cancelled, the computation will cancel any remaining child computations but will still wait for the other child computations to complete.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation that executes all the given asynchronous computations, initially queueing each as work items and using a fork/join pattern. If all child computations succeed, an array of results is passed to the success continuation. If any child computation raises an exception, then the overall computation will trigger an exception, and cancel the others. The overall computation will respond to cancellation while executing the child computations. If cancelled, the computation will cancel any remaining child computations but will still wait for the other child computations to complete.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation that executes all the given asynchronous computations sequentially. If all child computations succeed, an array of results is passed to the success continuation. If any child computation raises an exception, then the overall computation will trigger an exception, and cancel the others. The overall computation will respond to cancellation while executing the child computations. If cancelled, the computation will cancel any remaining child computations but will still wait for the other child computations to complete.
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Static member | Description | ||
Full Usage:
Async.AwaitEvent(event, ?cancelAction)
Parameters:
IEvent<'Del, 'T>
-
The event to handle once.
?cancelAction : unit -> unit
-
An optional function to execute instead of cancelling when a
cancellation is issued.
Returns: Async<'T>
An asynchronous computation that waits for the event to be invoked.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation that waits for a single invocation of a CLI event by adding a handler to the event. Once the computation completes or is cancelled, the handler is removed from the event.
The computation will respond to cancellation while waiting for the event. If a
cancellation occurs, and
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Full Usage:
Async.AwaitIAsyncResult(iar, ?millisecondsTimeout)
Parameters:
IAsyncResult
-
The IAsyncResult to wait on.
?millisecondsTimeout : int
-
The timeout value in milliseconds. If one is not provided
then the default value of -1 corresponding to Timeout.Infinite.
Returns: Async<bool>
An asynchronous computation that waits on the given IAsyncResult .
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The computation returns true if the handle indicated a result within the given timeout.
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![]() ![]() ![]() ![]() ![]() ![]() Return an asynchronous computation that will wait for the given task to complete and return its result.
If an exception occurs in the asynchronous computation then an exception is re-raised by this
function.
If the task is cancelled then Tasks.TaskCanceledException is raised. Note
that the task may be governed by a different cancellation token to the overall async computation
where the AwaitTask occurs. In practice you should normally start the task with the
cancellation token returned by
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![]() ![]() ![]() ![]() ![]() ![]() Return an asynchronous computation that will wait for the given task to complete and return its result.
If an exception occurs in the asynchronous computation then an exception is re-raised by this
function.
If the task is cancelled then Tasks.TaskCanceledException is raised. Note
that the task may be governed by a different cancellation token to the overall async computation
where the AwaitTask occurs. In practice you should normally start the task with the
cancellation token returned by
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Full Usage:
Async.AwaitWaitHandle(waitHandle, ?millisecondsTimeout)
Parameters:
WaitHandle
-
The WaitHandle that can be signalled.
?millisecondsTimeout : int
-
The timeout value in milliseconds. If one is not provided
then the default value of -1 corresponding to Timeout.Infinite.
Returns: Async<bool>
An asynchronous computation that waits on the given WaitHandle .
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The computation returns true if the handle indicated a result within the given timeout.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation that will sleep for the given time. This is scheduled using a System.Threading.Timer object. The operation will not block operating system threads for the duration of the wait.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation that will sleep for the given time. This is scheduled using a System.Threading.Timer object. The operation will not block operating system threads for the duration of the wait.
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Static member | Description |
Full Usage:
Async.CancelDefaultToken()
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![]() ![]() ![]() ![]() ![]() ![]() Raises the cancellation condition for the most recent set of asynchronous computations started without any specific CancellationToken. Replaces the global CancellationTokenSource with a new global token source for any asynchronous computations created after this point without any specific CancellationToken. |
Full Usage:
Async.CancellationToken
Returns: Async<CancellationToken>
An asynchronous computation capable of retrieving the CancellationToken from a computation
expression.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation that returns the CancellationToken governing the execution of the computation.
In
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![]() ![]() ![]() ![]() ![]() ![]()
Creates an asynchronous computation that executes
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Full Usage:
Async.DefaultCancellationToken
Returns: CancellationToken
The default CancellationToken.
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Full Usage:
Async.OnCancel(interruption)
Parameters:
unit -> unit
-
The function that is executed on the thread performing the
cancellation.
Returns: Async<IDisposable>
An asynchronous computation that triggers the interruption if it is cancelled
before being disposed.
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For example,
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Full Usage:
Async.StartChild(computation, ?millisecondsTimeout)
Parameters:
Async<'T>
-
The child computation.
?millisecondsTimeout : int
-
The timeout value in milliseconds. If one is not provided
then the default value of -1 corresponding to Timeout.Infinite.
Returns: Async<Async<'T>>
A new computation that waits for the input computation to finish.
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![]() ![]() ![]() ![]() ![]() ![]() Starts a child computation within an asynchronous workflow. This allows multiple asynchronous computations to be executed simultaneously.
This method should normally be used as the immediate
right-hand-side of a
When used in this way, each use of StartChild starts an instance of childComputation
and returns a completor object representing a computation to wait for the completion of the operation.
When executed, the completor awaits the completion of childComputation .
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Full Usage:
Async.TryCancelled(computation, compensation)
Parameters:
Async<'T>
-
The input asynchronous computation.
compensation : OperationCanceledException -> unit
-
The function to be run if the computation is cancelled.
Returns: Async<'T>
An asynchronous computation that runs the compensation if the input computation
is cancelled.
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![]() ![]() ![]() ![]() ![]() ![]()
Creates an asynchronous computation that executes
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Static member | Description |
Full Usage:
Async.SwitchToContext(syncContext)
Parameters:
SynchronizationContext
-
The synchronization context to accept the posted computation.
Returns: Async<unit>
An asynchronous computation that uses the syncContext context to execute.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation that runs its continuation using syncContext.Post. If syncContext is null then the asynchronous computation is equivalent to SwitchToThreadPool().
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Static member | Description |
Full Usage:
Async.AsBeginEnd(computation)
Parameters:
'Arg -> Async<'T>
-
A function generating the asynchronous computation to split into the traditional
.NET Asynchronous Programming Model.
Returns: ('Arg * AsyncCallback * obj -> IAsyncResult) * (IAsyncResult -> 'T) * (IAsyncResult -> unit)
A tuple of the begin, end, and cancel members.
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![]() ![]() ![]() ![]() ![]() ![]() Creates three functions that can be used to implement the .NET 1.0 Asynchronous Programming Model (APM) for a given asynchronous computation.
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Full Usage:
Async.FromBeginEnd(arg1, arg2, arg3, beginAction, endAction, ?cancelAction)
Parameters:
'Arg1
-
The first argument for the operation.
arg2 : 'Arg2
-
The second argument for the operation.
arg3 : 'Arg3
-
The third argument for the operation.
beginAction : 'Arg1 * 'Arg2 * 'Arg3 * AsyncCallback * obj -> IAsyncResult
-
The function initiating a traditional CLI asynchronous operation.
endAction : IAsyncResult -> 'T
-
The function completing a traditional CLI asynchronous operation.
?cancelAction : unit -> unit
-
An optional function to be executed when a cancellation is requested.
Returns: Async<'T>
An asynchronous computation wrapping the given Begin/End functions.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation in terms of a Begin/End pair of actions in the style used in .NET 2.0 APIs.
The computation will respond to cancellation while waiting for the completion
of the operation. If a cancellation occurs, and
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Full Usage:
Async.FromBeginEnd(arg1, arg2, beginAction, endAction, ?cancelAction)
Parameters:
'Arg1
-
The first argument for the operation.
arg2 : 'Arg2
-
The second argument for the operation.
beginAction : 'Arg1 * 'Arg2 * AsyncCallback * obj -> IAsyncResult
-
The function initiating a traditional CLI asynchronous operation.
endAction : IAsyncResult -> 'T
-
The function completing a traditional CLI asynchronous operation.
?cancelAction : unit -> unit
-
An optional function to be executed when a cancellation is requested.
Returns: Async<'T>
An asynchronous computation wrapping the given Begin/End functions.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation in terms of a Begin/End pair of actions in the style used in .NET 2.0 APIs.
The computation will respond to cancellation while waiting for the completion
of the operation. If a cancellation occurs, and
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Full Usage:
Async.FromBeginEnd(arg, beginAction, endAction, ?cancelAction)
Parameters:
'Arg1
-
The argument for the operation.
beginAction : 'Arg1 * AsyncCallback * obj -> IAsyncResult
-
The function initiating a traditional CLI asynchronous operation.
endAction : IAsyncResult -> 'T
-
The function completing a traditional CLI asynchronous operation.
?cancelAction : unit -> unit
-
An optional function to be executed when a cancellation is requested.
Returns: Async<'T>
An asynchronous computation wrapping the given Begin/End functions.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation in terms of a Begin/End pair of actions in the style used in .NET 2.0 APIs.
The computation will respond to cancellation while waiting for the completion
of the operation. If a cancellation occurs, and
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Full Usage:
Async.FromBeginEnd(beginAction, endAction, ?cancelAction)
Parameters:
AsyncCallback * obj -> IAsyncResult
-
The function initiating a traditional CLI asynchronous operation.
endAction : IAsyncResult -> 'T
-
The function completing a traditional CLI asynchronous operation.
?cancelAction : unit -> unit
-
An optional function to be executed when a cancellation is requested.
Returns: Async<'T>
An asynchronous computation wrapping the given Begin/End functions.
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![]() ![]() ![]() ![]() ![]() ![]() Creates an asynchronous computation in terms of a Begin/End pair of actions in the style used in CLI APIs.
The computation will respond to cancellation while waiting for the completion
of the operation. If a cancellation occurs, and
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