private void button1_Click(object sender, EventArgs e)
        {
            var t = new Thread(Do);
            t.IsBackground = true;
            t.Start();
        }

        private void Do()
        {
            int i = 0;
            while (true)
            {
                Thread.Sleep(1000);
                i++;
                Invoke(new Action(() => textBox1.Text = i.ToString()));
            }
        }