private Thread th = null;
private Thread thf = null;
private void button2_MouseDown(object sender,MouseEventArgs e)
{
 if(checkBox1.Checked)
 {
    thf = new Thread(new ThreadStart(file_transfer));  //file_transfer不执行
 }
 else
    m_PCNet.Set(3523,88);


  th = new Thread(new ThreadStart(step_for)); //step_for不执行
  th.Start();
}