title: Frozen windows form application with checkbox c#
body: <p>Here is my situation, when I check the checkbox, my application freezes but still works. Which means that it is still able to recognize data sent through the serial port; for testing purposes it just exits the application.</p>
  
  <p>If I comment out line 45 ("pipe = arduino.ReadLine();" see screenshot below) meaning that it no longer has to "ReadLine()", I am able to un-check the box. However now when I try to re-check the box, I get an error message saying <a href="http://i.stack.imgur.com/YcG5o.png" rel="nofollow">"Access to the port 'COM5' is denied"</a></p>
  
  <p>I assume that the code cannot continue because it is trying to "ReadLine()" when nothing has been sent through yet. However I do not have an explanation for being denied access to the COM port; rather than me trying to open the port when its already opened.</p>
  
  <pre><code>private void checkBox1_CheckedChanged(object sender, EventArgs e)
      {
  
          SerialPort arduino = new SerialPort();
          arduino.BaudRate = 9600;
          arduino.PortName = comboBox1.Text;
          string pipe;
  
          if (checkBox1.Checked)
          {
              checkBox1.Text = "Listening...";
              arduino.Open();
                  pipe = arduino.ReadLine();
                  if (pipe == "S\r")
                  {
                      //System.Diagnostics.Process.Start("shutdown", "/f /r /t 0");
                      System.Windows.Forms.Application.Exit();
                  }
          else
          {
              checkBox1.Text = "Start";
          }
      }
  }
  </code></pre>