for(int i=0;i<10;i++)
            {
                this.label1.Text = i.ToString();
            }  

        private delegate void SetLabelDelegate(DateTime dt);
        private void button2_Click(object sender, EventArgs e)
        {
            Thread th = new Thread(ShowCurrentTime);
            th.Start();
        }
        private void ShowCurrentTime()
        {
            while (true)
            {
                SetLabelValue(DateTime.Now);
                Thread.Sleep(1000);
            }
        }
        private void SetLabelValue(DateTime dt)
        {

            if (this.InvokeRequired)
            {
                this.Invoke(new SetLabelDelegate(SetLabelValue), new object[] { dt });
            }
            else
            {
                this.label1.Text = dt.ToString();
            }
        }