private void buttonStart_Click(object sender, EventArgs e)
        {
            (new Thread(new ThreadStart(() =>
            {
                while (!ThreadStop)
                {
                    System.Threading.Thread.Sleep(3000);
                    DoTask();
                }
            }
            ))).Start();
        }

        private void buttonStop_Click(object sender, EventArgs e)
        {
            ThreadStop = true;
        }

        void DoTask()
        {
            if (InvokeRequired)
            {
                BeginInvoke(new MethodInvoker(DoTask));
                return;
            }
            progressBar1.Value++;
        }