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ObjectDisposedException if USBtoSerial Port is unpluggedI'm writing an Application for a serial device, which is using a USB-to-Serial Converter. I'm polling that device for new data every 500 ms. So this is working fine. But if the customer unpluggs the USB-to-Serial Converter, I get an System.UnauthorizedAccessException on the next write operation and sometimes an ObjectDisposedException which is not chatchable after that. I tried many things and I can reproduce it now with some very simple lines of code. First I have to explain, that my System - after playing a lot with plugging and unplugging USB-to-Serial devices - sometimes takes a few seconds until it recognizes the device to be unplugged. So I have a few seconds between unplugging the device and hearing the unplug sound of the system. Now my simple example: In a Windows Form, I create a SerialPort and open that port. Now I unplugg the USB-to-Serial converter. Then I close the SerialPort (before the unplugg sound is played) Then, after a few seconds, exactly when the unplugged sound is played, I get that "ObjectDisposedException, safe handle has been closed". I also tried to create a new port instead of closing it. In this case I get the UnauthorizedAccessException when the unplugged sound is played - or when the form is closed. As I figured out, if any command of the SerialPort is called between unplugging the device and the unplugg sound of the system, a not catchable exception will be thrown. How can I avoid that Exception? Or is it possible to catch (and ignor) it? Thanks in advance. Robert Hello Robert,
I think it is impossible to avoid of the problem, since it is a hardware issue, and .NET application totally reply on windows system to recognize and connect to the Serial port. We may find some way to catch the exceptions, and tell the user to check their device. For example, in Application.ThreadException event. In the application, we cannot expect when user will unplug it or put it back, so it is hard to close/ reopen the port to avoid the application. We may catch the exception Application.ThreadException and tell customer there may be an error with the USB-to-Serial converter. And, for such a hardware change, we had better recommend user quit current application and enter again. Sincerely, Luke Zhang Microsoft Online Community Support ================================================== Get notification to my posts through email? Please refer to http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif ications. Note: The MSDN Managed Newsgroup support offering is for non-urgent issues where an initial response from the community or a Microsoft Support Engineer within 1 business day is acceptable. Please note that each follow up response may take approximately 2 business days as the support professional working with you may need further investigation to reach the most efficient resolution. The offering is not appropriate for situations that require urgent, real-time or phone-based interactions or complex project analysis and dump analysis issues. Issues of this nature are best handled working with a dedicated Microsoft Support Engineer by contacting Microsoft Customer Support Services (CSS) at http://msdn.microsoft.com/subscriptions/support/default.aspx. ================================================== This posting is provided "AS IS" with no warranties, and confers no rights. Hello Luke,
unfortunately, the Application.ThreadException will not catch this exception. Well, the AppDomain.CurrentDomain.UnhandledException will do, but after that, I cannot avoid that the application is terminated immediately. Do you see any chance to avoid the termination of the application? (The place where this exception occures is absolutley uncritical for the application). Sincerely, Robert Hello Robert,
Thank you for the update. AppDomain.CurrentDomain.UnhandledException can catch an exception, but the exception will be still raised after that. So that the application is terminated immediately. Sincerely, Luke Zhang Microsoft Online Community Support This posting is provided "AS IS" with no warranties, and confers no rights. I was looking at the ability to switch from using interop (for serial comm)
in our application to using the SerialPort class. However, the appearent inability for the class to deal with removeable comm ports (and shutting down the app) will definitely prevent it. Considering how many PC's no longer have built in serial ports, the inability to deal with the port going away really makes this class unusable for any non trivial use. When using InterOp to access the Win32 functions WaitCommEvent() and SetCommMask(), unplugging the USB port does not result in an exception that causes an application shutdown. The receivers WaitCommEvent call simply returns without showing any data has been received. Then calling SetCommMask to reset the event mask returns a failure, which allows the application to know the comm port is no longer available. MS really needs to look at fixing this. With the effort that has been put into the creation of the SerialPort class, leaving it in this state would be a real waste. Ken Show quote "Luke Zhang [MSFT]" wrote: > Hello Robert, > > I think it is impossible to avoid of the problem, since it is a hardware > issue, and .NET application totally reply on windows system to recognize > and connect to the Serial port. > > We may find some way to catch the exceptions, and tell the user to check > their device. For example, in Application.ThreadException event. In the > application, we cannot expect when user will unplug it or put it back, so > it is hard to close/ reopen the port to avoid the application. We may catch > the exception Application.ThreadException and tell customer there may be > an error with the USB-to-Serial converter. And, for such a hardware change, > we had better recommend user quit current application and enter again. > > Sincerely, > > Luke Zhang > > Microsoft Online Community Support > ================================================== > Get notification to my posts through email? Please refer to > http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif > ications. > > Note: The MSDN Managed Newsgroup support offering is for non-urgent issues > where an initial response from the community or a Microsoft Support > Engineer within 1 business day is acceptable. Please note that each follow > up response may take approximately 2 business days as the support > professional working with you may need further investigation to reach the > most efficient resolution. The offering is not appropriate for situations > that require urgent, real-time or phone-based interactions or complex > project analysis and dump analysis issues. Issues of this nature are best > handled working with a dedicated Microsoft Support Engineer by contacting > Microsoft Customer Support Services (CSS) at > http://msdn.microsoft.com/subscriptions/support/default.aspx. > ================================================== > > This posting is provided "AS IS" with no warranties, and confers no rights. > > > >  |
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