if (general.backgroundWorker1.CancellationPending)
{
   return;
}

private void button4_Click(object sender, EventArgs e) //button invokes heavy function
{
    if (!backgroundWorker1.IsBusy)
        backgroundWorker1.RunWorkerAsync();
}

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    heavyFunction(this);
    if (backgroundWorker1.CancellationPending)
    {
        e.Cancel = true;
        return;
    }
}

private void backgroundWorker1_RunWorkerCompleted_1(object sender, RunWorkerCompletedEventArgs e)
{
    if (e.Cancelled)
    {
        statusLabel.Text = "Status: cancelled";
    }
    else if (e.Error != null)
    {
        statusLabel.Text = "ERROR!";
    }
    else
    {
        some code;
    }
}

private void cancelSDoutLoop_Click(object sender, EventArgs e)
{
    if (backgroundWorker1.IsBusy)
    {
        backgroundWorker1.CancelAsync();
    }
}

Delay(TimeSpan)

Delay(TimeSpan, CancellationToken)