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


The .NET API Reference documentation has a new home. Visit the .NET API Browser on docs.microsoft.com to see the new experience.

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 Task ContinueWith(
	Action<Task> continuationAction,
	TaskContinuationOptions continuationOptions


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.

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

The continuationAction argument is null.


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 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; } }

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