Serial Port problem

Question

I am writing an application that listens to a serial port(COM1) for input from a barcode scanner. The problem I am having is when I move between different forms. In the form load event on each form, I set the port name:

serialPort.PortName = "COM1"

to the correct COM port. Whenever I am ready to move to another form, I call:

serialPort.Close()
serialPort.Dispose()

However, when I open the next form, I get the "access denied" error when trying to open the port again.

I am using the SerialPort control on the form rather than programmatically creating a serialPort.

Gary · Answer

I had the same problem and I now have it working. You have two forms....say main and child. You run fine in the child using the serial port. You exit the child and when you come back in you get the access denied message. This is the problem that I had What you need to do in the child form is select the form and then click on properties pane. Choose event listing double click on formClosing Note...Not form closed but form closing. add code to close the serial port. This worked for me. Bottom Line : The port needs to be closed BEFORE you exit or close the form. When or how you do that is up to you. I just found it more easy to do it in the formclosing event.

Ryan Alford · Answer

Tried #1 still get the error message. Tried #2 now I get the error message when I try to open the port on the second form.

Alan · Answer

There are a couple of other approachs which might be worth a try: 1. Don't call Dispose() on the SerialPort object just Close(). 2. Use the same SerialPort object for both forms. If you add this to Form1 in the designer change the access to public. Then in Form2 you can access it with code like the following: Form1 form1 = (Form1)Application.OpenForms[Form1]; form1.serialPort1.Open();

Ryan Alford · Answer

I just tried creating the serialPort programmatically which would allow me to create a new serialPort object on each form load(on both forms). However I still get the same error message when trying open the port again on the first form.

Ryan Alford · Answer

with me creating the serialPort by using a control on the form instead of creating it programmatically if I create the serialPort again it doesn't seem to work at all.

Alan · Answer

When you go back to Form1 are you creating another SerialPort object bearing in mind that you disposed of the previous one? The previous object may not yet have been garbage collected but be hanging around in an unstable state.

Ryan Alford · Answer

I tried that didn't work. this works fine: Open Form1 open port close port Open Form2 open port hide Form1 .... my problem occurs here: open Form1 open port close port Open Form2 open port hide Form1 .... close port Open Form1 open port close Form2 the problem happens when I open the port on a form where the port was previously opened.

Alan · Answer

I'd try inserting a delay between closing the port on one form and opening it on another as the port may need a little time to close properly.