Task.ContinueWith Method (Action(Of Task), TaskContinuationOptions)

 

Creates a continuation that executes when the target task completes according to the specified TaskContinuationOptions.

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

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

Parameters

continuationAction
Type: System.Action(Of Task)

An action to run according to the specified continuationOptions. When run, the delegate will be passed the completed task as an argument.

continuationOptions
Type: System.Threading.Tasks.TaskContinuationOptions

Options for when the continuation is scheduled and how it behaves. This includes criteria, such as OnlyOnCanceled, as well as execution options, such as ExecuteSynchronously.

Return Value

Type: System.Threading.Tasks.Task

A new continuation Task.

Exception Condition
ArgumentNullException

The continuationAction argument is null.

ArgumentOutOfRangeException

The continuationOptions argument specifies an invalid value for TaskContinuationOptions.

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.

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.)


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

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 5.0
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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