CancellationTokenSource is not working

I have a producer-consumer application, I wrote it as a WPF. For the convince, I set the project's property as console, so I can simply using Console output.

Basically I add integers to a BufferBlock queue in producer, when I click the Start button, it runs producer and consumer. Now I want to cancel it by clicking cancel button then displaying "Stop" . So I passed CancellationToken to the method but it is not working, which means it keeps send the output.

The main code:

public static BufferBlock<int> queue = new BufferBlock<int>(new DataflowBlockOptions { BoundedCapacity = 1000 });
private CancellationTokenSource cTokenSource;
private static CancellationToken cToken;

 private void Start_Click(object sender, RoutedEventArgs e)
        {
            cTokenSource = new CancellationTokenSource();
            cToken = cTokenSource.Token;
            var producer = Producer();
            var consumer = Consumer();

        }

async Task Consumer()
        {
            var executionDataflowBlockOptions = new ExecutionDataflowBlockOptions
            {
                MaxDegreeOfParallelism = 1,
                CancellationToken = cToken
            };
            var consumerBlock = new ActionBlock<int>(
i =>
{
    if (cToken.IsCancellationRequested)
        return;
    RunScript(i, cToken); Dispatcher.BeginInvoke((Action)delegate()
    {
        items.Add(new TodoItem() { Number = i });
    });
},
executionDataflowBlockOptions);

            queue.LinkTo(
consumerBlock, new DataflowLinkOptions { PropagateCompletion = true });
            await consumerBlock.Completion;
        }

        private void RunScript(int i, CancellationToken cToken)
        {
            Console.WriteLine("Processing " + i);
            for (int j = 0; j < 100; j++)
            {
                Console.WriteLine(j);
                 Thread.Sleep(1000);
            }
            Console.WriteLine("------------");
            cToken.Register(() =>
                   {
                       Console.WriteLine("Stop");
                       return;
                   });
        }

        private void Cancel_Click(object sender, RoutedEventArgs e)
        {
            cTokenSource.Cancel();
        }

I also provided a full clean solution on the OneDrive.

The file name is "CancellationTokenIsNotWorking.zip". Thanks for help.