informs about a pending cancelation
This will be set to true, if an algorithm is running and the user of the class called the Cancel(Int32) method.
Class designer of derived classes should frequently check this property. If a cancellatioin was requested, the algorithm should close as fast as possible. This is the 'good way' out of the algorithm. If the algorithm does not respond fast enough, the user might kill the thread, which will not give the algorithm the chance to exit cleanly.