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

Creates a continuation that executes according to the specified TaskContinuationOptions.

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

public Task ContinueWith(
	Action<Task> continuationAction,
	CancellationToken cancellationToken,
	TaskContinuationOptions continuationOptions,
	TaskScheduler scheduler
)

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.

cancellationToken
Type: System.Threading.CancellationToken

The CancellationToken that will be assigned to the new continuation task.

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.

scheduler
Type: System.Threading.Tasks.TaskScheduler

The TaskScheduler to associate with the continuation task and to use for its execution.

Return Value

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

ExceptionCondition
ObjectDisposedException

The CancellationTokenSource that created the token has already been disposed.

ArgumentNullException

The continuationAction argument is null.

-or-

The scheduler 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 criteria specified through the continuationOptions parameter are not met, the continuation task will be canceled instead of scheduled.

The following is an example of using ContinueWith to run work both in the background and on the user interface threads.

private void Button1_Click(object sender, EventArgs e)
{
   var backgroundScheduler = TaskScheduler.Default;
   var uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();
   Task.Factory.StartNew(delegate { DoBackgroundComputation(); },
                         backgroundScheduler).
   ContinueWith(delegate { UpdateUI(); }, uiScheduler).
                ContinueWith(delegate { DoAnotherBackgroundComputation(); },
                             backgroundScheduler).
                ContinueWith(delegate { UpdateUIAgain(); }, uiScheduler);
}

.NET Framework

Supported in: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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