private  int leftTime = 5;
        private void timer1_Tick(object sender, EventArgs e)
        {
            button.Enabled = false;            
            if (leftTime >= 10)
            {
                this.label1.Text = leftTime.ToString();
                button.Text 
 
= "撥號 （請稍後0" + leftTime.ToString() + ")";
            }
            else
            {
                this.label1.Text = "撥號 0" + leftTime.ToString();
                button.Text = "撥號 （請稍後0" + leftTime.ToString() + ")";
            }
            if (leftTime == 0)
            {
                //倒計時到“00”，計時器停止
 

                this.timer1.Stop();
                //去做其他事情
                //......
                button.Enabled = true;
                timer1.Enabled = false;
                this.label1.Text = "";
                button.Text = "撥號";
                leftTime = 5;
            }
            else
            {
                leftTime
 
--;
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            timer1.Enabled = true;
        }

winform界面button倒計時