Hi,

Since the My.Application.UnhandledException can only be used in VB2005
winform project, I am assuming that you are using .Net Winform.

I have created a sample "UnhandledExceptionTestVB" winform project in
VB2005. In the sample, I throw the exception in Button_Click event:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
       Throw New Exception("this is a test")
   End Sub

Also, I handled the My.Application.UnhandledException in
ApplicationEvents.vb file below:

Namespace My
   Partial Friend Class MyApplication

       Private Sub MyApplication_UnhandledException(ByVal sender As
Object, ByVal e As
Microsoft.VisualBasic.ApplicationServices.UnhandledExceptionEventArgs)
Handles Me.UnhandledException

           MessageBox.Show(Environment.StackTrace)
           e.ExitApplication = True

       End Sub
   End Class
End Namespace

After dismiss the messagebox from the MyApplication_UnhandledException, my
test winform application will terminate silently without any error message
box titled with "System Error". So it seems that your application has
different behavior with my test project. Is it possible for you to create a
little sample project to help me reproduce this problem? Then it would be
more efficient for me to troubleshoot the root cause.

Additionally, can you be specific what "End" method you are calling in your
application? I can not find this method on UnhandledExceptionEventArgs
class.

Finally, here is some additional information:

My.Application.UnhandledException is actually an extra facility introduced
by VB2005, which is not available from other languages. Actually it is very
different from AppDomain.UnhandledException event.
AppDomain.UnhandledException event is a CLR notification which is called
whenever an unhandled exception is generated in the AppDomain. Note:
AppDomain.UnhandledException event is merely a notification, you can not
use AppDomain.UnhandledException to tell CLR to dismiss the exception and
continue execute. The CLR will always shutdown the AppDomain after
AppDomain.UnhandledException event.

My.Application.UnhandledException is actually more like
Application.ThreadException event in .Net Winform. Actually, this event is
called by a pre-registered Application.ThreadException handler of VB2005.
To prove this, you may examine the call stack in
My.Application.UnhandledException event handler, see below:

   
UnhandledExceptionTestVB.exe!UnhandledExceptionTestVB.My.MyApplication.MyApp
lication_UnhandledException    Basic
   
Microsoft.VisualBasic.dll!Microsoft.VisualBasic.ApplicationServices.WindowsF
ormsApplicationBase.raise_UnhandledException    Basic
   
Microsoft.VisualBasic.dll!Microsoft.VisualBasic.ApplicationServices.WindowsF
ormsApplicationBase.OnUnhandledException    Basic
   
Microsoft.VisualBasic.dll!Microsoft.VisualBasic.ApplicationServices.WindowsF
ormsApplicationBase.OnUnhandledExceptionEventAdaptor    Basic
   
System.Windows.Forms.dll!System.Windows.Forms.Application.ThreadContext.OnTh
readException    C#
    System.Windows.Forms.dll!System.Windows.Forms.Control.WndProcException    C#
   
System.Windows.Forms.dll!System.Windows.Forms.Control.ControlNativeWindow.On
ThreadException    C#
    System.Windows.Forms.dll!System.Windows.Forms.NativeWindow.Callback    C#
    [Native to Managed Transition]   
    [Managed to Native Transition]   
   
System.Windows.Forms.dll!System.Windows.Forms.Application.ComponentManager.S
ystem.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoo
p    C#
   
System.Windows.Forms.dll!System.Windows.Forms.Application.ThreadContext.RunM
essageLoopInner    C#
   
System.Windows.Forms.dll!System.Windows.Forms.Application.ThreadContext.RunM
essageLoop    C#
    System.Windows.Forms.dll!System.Windows.Forms.Application.Run    C#
   
Microsoft.VisualBasic.dll!Microsoft.VisualBasic.ApplicationServices.WindowsF
ormsApplicationBase.OnRun    Basic
   
Microsoft.VisualBasic.dll!Microsoft.VisualBasic.ApplicationServices.WindowsF
ormsApplicationBase.DoApplicationModel    Basic
   
Microsoft.VisualBasic.dll!Microsoft.VisualBasic.ApplicationServices.WindowsF
ormsApplicationBase.Run    Basic

As you can see, "OnThreadException" upper in the stack calls
MyApplication_UnhandledException finally.

Note: this is just more information. It still can not explain why there is
an extra "System Error" message box generated in your project. A little
sample project is still useful for me to debug the root cause. I will wait
for it.

Thanks.

Best regards,
Jeffrey Tan
Microsoft Online Community Support
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