CancellationToken.Register Method (Action(Of Object), Object)


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

Registers a delegate that will be called when this CancellationToken is canceled.

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

Public Function Register (
	callback As Action(Of Object),
	state As Object
) As CancellationTokenRegistration


Type: System.Action(Of Object)

The delegate to be executed when the CancellationToken is canceled.

Type: System.Object

The state to pass to the callback when the delegate is invoked. This may be null.

Return Value

Type: System.Threading.CancellationTokenRegistration

The CancellationTokenRegistration instance that can be used to deregister the callback.

Exception Condition

The associated CancellationTokenSource has been disposed.


callback is null.

If this token is already in the canceled state, the delegate will be run immediately and synchronously. Any exception the delegate generates will be propogated out of this method call.

The current ExecutionContext, if one exists, will be captured along with the delegate and will be used when executing it.

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