Explanation
The CancellationToken.ThrowIfCancellationRequested method throws a OperationCanceledException if this token has had cancellation requested.
This method provides functionality equivalent to:
C#
if (token.IsCancellationRequested)
throw new OperationCanceledException(token);
Reference: CancellationToken.ThrowIfCancellationRequested Method ()
https://msdn.microsoft.com/en-us/library/system.threading.cancellationtoken.throwifcancellationrequested(v=vs.