How to reset a CancellationToken properly?

Question

I have been playing round with the Async CTP this morning and have a simple program with a button and a label. Click the button<

Answer 1

I had the same problem and I figured it out that the best way to solve it is to create cancellation token source newly just before calling the method.

this is what I do on my start button click:

cancellationTokenSource = new CancellationTokenSource();
cancellationToken = cancellationTokenSource.Token;
Task.Factory.StartNew(StartUpload, cancellationToken);

I change the caption for the same button to cancel and when a click occurs on cancel, I call

cancellationTokenSource.Cancel();

Here is the full code:

if (button3.Text != "&Start Upload")
{
    cancellationTokenSource.Cancel();
}
else
{
    try
    {
        cancellationTokenSource = new CancellationTokenSource();
        cancellationToken = cancellationTokenSource.Token;
        Task.Factory.StartNew(StartUpload, cancellationToken);
    }
    catch (AggregateException ex)
    {
        var builder = new StringBuilder();
        foreach (var v in ex.InnerExceptions)
            builder.Append("\r\n" + v.InnerException);
        MessageBox.Show("There was an exception:\r\n" + builder.ToString());
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}