The CancellationTokenExtensions type provides a single extension method for CancellationToken: AsTask, which returns a task that will enter the Canceled state when the CancellationToken is signaled. If the CancellationToken is never signaled, the returned task will never complete.

public static class CancellationTokenExtensions
{
  // Returns a Task that is canceled when this CancellationToken is canceled.
  public static Task AsTask(this CancellationToken cancellationToken);
}

The full API is supported on all platforms.