How to do robust SerialPort programming with .NET / C#?

Question

I\'m writing a Windows Service for communication with a Serial Mag-stripe reader and a relay board (access control system).

I run into problems where the code stops

Answer 1

You can't close someone elses connection to a port, the following code will never work:

if (serialPort.IsOpen) serialPort.Close();

Because your object didn't open the port you can't close it.

Also you should close and dispose the serial port even after exceptions occur

try
{
   //do serial port stuff
}
finally
{
   if(serialPort != null)
   {
      if(serialPort.IsOpen)
      {
         serialPort.Close();
      }
      serialPort.Dispose();
   }
}

If you want the process to be interruptible then you should Check if the port is open and then back off for a period and then try again, something like.

while(serialPort.IsOpen)
{
   Thread.Sleep(200);
}