• Article

Task.ContinueWith Method (Action<Task>, TaskContinuationOptions)

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Creates a continuation that executes according to the specified TaskContinuationOptions.

Namespace:  System.Threading.Tasks
Assembly:  mscorlib (in mscorlib.dll)

Syntax

'Declaration
Public Function ContinueWith ( _
    continuationAction As Action(Of Task), _
    continuationOptions As TaskContinuationOptions _
) As Task

public Task ContinueWith(
    Action<Task> continuationAction,
    TaskContinuationOptions continuationOptions
)

Parameters

  • continuationAction
    Type: System.Action<Task>
    An action to run according to the specified continuationOptions. When run, the delegate will be passed the completed task as an argument.

Return Value

Type: System.Threading.Tasks.Task
A new continuation Task.

Exceptions

Exception Condition
ObjectDisposedException

The Task has been disposed.
ArgumentNullException

The continuationAction argument is null.
ArgumentOutOfRangeException

The continuationOptions argument specifies an invalid value for TaskContinuationOptions.

Remarks

The returned Task will not be scheduled for execution until the current task has completed. If the continuation criteria specified through the continuationOptions parameter are not met, the continuation task will be canceled instead of scheduled.

Examples

The following example demonstrates using TaskContinuationOptions to specify that a continuation task should run synchronously when the antecedent task completes. (If the specified task has already completed by the time ContinueWith is called, the synchronous continuation will run on the thread calling ContinueWith.)

// C#

public class TaskCounter

{

private volatile int _count;

public void Track(Task t)

{

if (t == null) throw new ArgumentNullException("t");

Interlocked.Increment(ref _count);

t.ContinueWith(ct => Interlocked.Decrement(ref _count), TaskContinuationOptions.ExecuteSynchronously);

}

public int NumberOfActiveTasks { get { return _count; } }

}

' Visual Basic

Public Class TaskCounter

Private _count as Integer

Public Sub Track(ByVal t as Task)

If t is Nothing Then Throw New ArgumentNullException("t")

Interlocked.Increment(_count)

t.ContinueWith(Sub(ct)

Interlocked.Decrement(_count)

End Sub, TaskContinuationOptions.ExecuteSynchronously)

End Sub

Public ReadOnly Property NumberOfActiveTasks As Integer

Get

Return _count

End Get

End Property

End Class

Version Information

Silverlight

Supported in: 5

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.