winforms application unexpectedly crashes

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Hi,

I've a winforms applicatoin (a big one with 1 mdi and about 100+ forms). I've added code in applicationevents.vb to handle the unhandled exceptions.

VB

Namespace My
    Partial Friend Class MyApplication

        Private Sub MyApplication_UnhandledException(ByVal sender As Object, ByVal e As Microsoft.VisualBasic.ApplicationServices.UnhandledExceptionEventArgs) Handles Me.UnhandledException
            e.ExitApplication = False
            IO.File.AppendAllText("error.txt", Format(Now, "dd-MMM-yyyy HH:mm:ss") & " - Unex - " & e.Exception.Message & vbCrLf & _
                                  e.Exception.StackTrace & vbCrLf)
            MessageBox.Show("got error")
        End Sub

    End Class

End Namespace

Here I'm able to get the message box, and the exception details written to the txt file. But the application closes, even though I explicitly coded ExitApplication to False.

When I test the scenario in a simple winform, it works fine. But in this project , I'm facing this problem. Is there any special configuration I'm missing out?

Any help/ idea greatly appreciated.

Posted 9-Jan-14 2:21am

thams

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Sergey Alexandrovich Kryukov · Accepted Answer · 2014-01-09T06:49:00

Solution 1

This is not how you should do it. You need to handle all exceptions in every outer event handling loop of the application. For this purpose, System.Windows.Forms.Application class has the following facility:
http://msdn.microsoft.com/en-us/library/system.windows.forms.application.onthreadexception%28v=vs.110%29.aspx[^],
http://msdn.microsoft.com/en-us/library/system.threading.threadexceptioneventhandler%28v=vs.110%29.aspx[^],
http://msdn.microsoft.com/en-us/library/system.threading.threadexceptioneventargs%28v=vs.110%29.aspx[^],
see also http://msdn.microsoft.com/en-us/library/ms157905(v=vs.110).aspx[^],
or http://msdn.microsoft.com/en-us/library/ms223898(v=vs.110).aspx[^].

First of all, in your entry-point method (Main), you need to set up this mode:

VB

Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException)
' see other values of this enum

And then, install an exception handler for the event Application.OnThreadException somewhere. I usually do it in the constructor of the main form, in the very beginning, just to use some form methods in the handler, but it could be done anywhere else, as soon as possible. The event arguments class System.Threading.ThreadExceptionEventArgs gives your the access to the exception instance (ThreadExceptionEventArgs.Exception). The sample code can be found here:
http://msdn.microsoft.com/en-us/library/system.threading.threadexceptioneventargs%28v=vs.110%29.aspx[^].

—SA

Posted 9-Jan-14 6:49am

Sergey Alexandrovich Kryukov

Updated 9-Jan-14 7:04am

v4

Comments

CHill60 9-Jan-14 13:02pm

5'd!

Sergey Alexandrovich Kryukov 9-Jan-14 13:04pm

Thank you very much,
—SA

[no name] 9-Jan-14 14:44pm

Learning++

Sergey Alexandrovich Kryukov 9-Jan-14 23:33pm

Thank you.
—SA

thams 10-Jan-14 1:00am

Hi,
Thanks for the bunch of tech stuffs.
I've identified my problem. Just made the jit debugger = true in the app config file. This was the culprit. Making it false (or simply delete the line) solved the problem.
Thanks anyway.

Sergey Alexandrovich Kryukov 10-Jan-14 1:45am

JIT debugger — very interesting. You see, it's good that you solved the problem and prevented some exception, but this is not enough. You really need to use the technique I described anyway, because you may have some other unhandled exceptions and also because some exceptions could not be prevented in principle; and you don't want to have them unhandled and leave the user with no informative exception information. Moreover, you need to handle all exceptions on the top stack frame of the stack of each and every thread.

So, will you accept my answer formally (green "Accept" button)?

—SA

thams 10-Jan-14 2:17am

Yes. as u said its important to handle all exceptions. In my case, this much is enough and I dont want to show any annoying error information to the user. So I'm just showing a nice error window with generic message, and in background capturing all error info into a text file.

Sergey Alexandrovich Kryukov 10-Jan-14 4:51am

Showing nice informative message is better than annoying, and both is much better than not showing anything. If you conceal some "natural" system, hardware exceptions, it prevents the user from taking appropriate actions, and not showing your bugs is just counter-productive (or I call it dishonest) way of doing the work. And not handling exceptions would cause an ugly and non-informative message from OS. Overall, handling all the exceptions at least on the very top (and, for UI, in the cycle) is unavoidable for any application which is supposed to be at least professional.

Good luck, call again.
—SA

thams · Accepted Answer · 2014-01-09T19:04:00

Solution 2

In the app.config file

HTML

<system.windows.forms jitdebugging="true" />

I coundn't remember when I've added this. Making it to false solved the problem.

Posted 9-Jan-14 19:04pm

thams