Task.ContinueWith Method (Action<Task>, CancellationToken, TaskContinuationOptions, TaskScheduler)
Microsoft Silverlight will reach end of support after October 2021. Learn more.
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), _
cancellationToken As CancellationToken, _
continuationOptions As TaskContinuationOptions, _
scheduler As TaskScheduler _
) As Task
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.
Exceptions
| Exception | Condition |
|---|---|
| ObjectDisposedException | The Task has been disposed. -or- 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. |
Remarks
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.
Examples
The following is an example of using ContinueWith to run work both in the background and on the user interface threads.
// C#
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);
}
' Visual Basic
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim backgroundScheduler = TaskScheduler.Default
Dim uiScheduler = TaskScheduler.FromCurrentSynchronizationContext()
Task.Factory.StartNew(Sub()
DoBackgroundComputation()
End Sub, backgroundScheduler).ContinueWith(Sub(t)
UpdateUI()
End Sub, uiScheduler).ContinueWith(Sub(t)
DoAnotherBackgroundComputation()
End Sub, backgroundScheduler).ContinueWith(Sub(t)
UpdateUIAgain()
End Sub, uiScheduler)
End Sub
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.