private void bgw_PLC_DoWork(object sender, DoWorkEventArgs e)
        {
            while (!bgw_PLC.CancellationPending)
            {
                if (bgw_PLC.CancellationPending)
                {
                    e.Cancel = true;
                }                if (this.textBox1.Text == "1")   
                {
                    //执行start按钮
                    button1_Click(sender, e);
                    bgw_PLC.CancelAsync();                    //开始计时
                    timerPLCStart = System.DateTime.Now;
                    timer1.Enabled = true;
                }
            }
        }
我用timer1.Enabled = true;去开启PLC为什么无效?
请教原因