System.NullReference exception

**Armin Zingler** · Oct 16 '08, 11:55 AM

Re: System.NullRefe rence exception

"Steve" <ga630sf@nospam .nospamschrieb

Hi All
>
I have a windows forms Application (SAM) in vb.net 2008 using .net
framework V2
>
One and only one customer out of 30 customers is getting errors
daily where they have to close and restart my application, sometimes
several times a day
>
The customer has XP Home SP2
>
The event viewer shows the following although not always in the same
sequence
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4 sam, P5
1.0.0.0, P6 48d969a4, P7 5, P8 0, P9 system.nullrefe renceexception,
P10 NIL.
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4
microsoft.visua lbasic, P5 8.0.0.0, P6 471ee7ea, P7 86, P8 a2, P9
system.componen tmodel.win32, P10 NIL.
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48eea25c, P4
microsoft.visua lbasic, P5 8.0.0.0, P6 471ee7ea, P7 5e, P8 1e1, P9
34ssps20bdj3nj0 wmit5kamzhvglfz cc, P10 NIL.
>
Hanging application SAM.exe, version 1.0.0.0, hang module hungapp,
version 0.0.0.0, hang address 0x00000000.
>
I am lost as to what may be causing it and like I said it only
happens to the 1 customer
>
Any ideas what it could be and any ideas on how to troubleshoot it
further to find the exact cause?

How does you exception handling code look like?

Armin

**kimiraikkonen** · Oct 16 '08, 03:35 PM

Re: System.NullRefe rence exception

On Oct 16, 1:53 pm, "Steve" <ga63...@nospam .nospamwrote:

Hi All
>
I have a windows forms Application (SAM) in vb.net 2008 using .net framework
V2
>
One and only one customer out of 30 customers is getting errors daily where
they have to close and restart my application, sometimes several times a day
>
The customer has XP Home SP2
>
The event viewer shows the following although not always in the same
sequence
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4 sam, P5 1.0.0.0,
P6 48d969a4, P7 5, P8 0, P9 system.nullrefe renceexception, P10 NIL.
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4
microsoft.visua lbasic, P5 8.0.0.0, P6 471ee7ea, P7 86, P8 a2, P9
system.componen tmodel.win32, P10 NIL.
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48eea25c, P4
microsoft.visua lbasic, P5 8.0.0.0, P6 471ee7ea, P7 5e, P8 1e1, P9
34ssps20bdj3nj0 wmit5kamzhvglfz cc, P10 NIL.
>
Hanging application SAM.exe, version 1.0.0.0, hang module hungapp, version
0.0.0.0, hang address 0x00000000.
>
I am lost as to what may be causing it and like I said it only happens to
the 1 customer
>
Any ideas what it could be and any ideas on how to troubleshoot it further
to find the exact cause?
>
Regards
Steve

First try to have "try-catch" exception handling blocks as many as
possible in your project to catch "possible" exceptions, then based on
your description, make sure you have a exception block in form_load
and form_formclosed and formClosing events like:

' When the form is loaded
Private Sub Form1_Load(.... .) Handles MyBase.Load

Try

' Do the stuff

Catch ex As Exception
Msgbox(ex.Messs age)

End Try

End Sub

....do the same for form's FormClosing and FormClosed events if your
application is not console one.

Additionaly, related to "System.NullRef erence" exception, presumably,
your variable may have no value assigned to the referenced object
anylonger as the reason of exception. Or the object is being
instantianted improperly after app restart.

Just it was a guess,

Onur Güzel

**Patrice** · Oct 16 '08, 05:15 PM

Re: System.NullRefe rence exception

The first step would be to have a callstack so that you can see where it
happens. You could start by adding a global exception handler (if not
already done) in the appplication that would store somewhere exception
details to ease further analysis...

---
Patrice

"Steve" <ga630sf@nospam .nospama écrit dans le message de groupe de
discussion : uwEjx13LJHA.173 6@TK2MSFTNGP03. phx.gbl...

Hi All
>
I have a windows forms Application (SAM) in vb.net 2008 using .net
framework V2
>
One and only one customer out of 30 customers is getting errors daily
where they have to close and restart my application, sometimes several
times a day
>
The customer has XP Home SP2
>
The event viewer shows the following although not always in the same
sequence
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4 sam, P5
1.0.0.0, P6 48d969a4, P7 5, P8 0, P9 system.nullrefe renceexception, P10
NIL.
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4
microsoft.visua lbasic, P5 8.0.0.0, P6 471ee7ea, P7 86, P8 a2, P9
system.componen tmodel.win32, P10 NIL.
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48eea25c, P4
microsoft.visua lbasic, P5 8.0.0.0, P6 471ee7ea, P7 5e, P8 1e1, P9
34ssps20bdj3nj0 wmit5kamzhvglfz cc, P10 NIL.
>
Hanging application SAM.exe, version 1.0.0.0, hang module hungapp, version
0.0.0.0, hang address 0x00000000.
>
I am lost as to what may be causing it and like I said it only happens to
the 1 customer
>
Any ideas what it could be and any ideas on how to troubleshoot it further
to find the exact cause?
>
Regards
Steve
>
>
>

**Steve** · Oct 16 '08, 10:05 PM

Re: System.NullRefe rence exception

Hi All

Thanks for the responses

I have try/catch blocks in most of my routines

I also have a code in MyApplication_U nhandledExcepti onroutine, which doesn't
fire (see below)

'writes unhandled exceptions to my log file

mymsgbox(e.Exce ption.Message & vbCr & e.Exception.Inn erException.ToS tring)

If e.Exception.Mes sage.Length 200 Then

savetolog("Auto ", e.Exception.Mes sage.Substring( 0, 199))

Else

savetolog("Auto ", e.Exception.Mes sage)

End If

The screen they get when the error occurs is not the usual .net screen
showing the error details, but the Microsoft screen with send report / don't
send buttons

Not sure if this makes a difference

Regards

Steve

"Steve" <ga630sf@nospam .nospamwrote in message
news:uwEjx13LJH A.1736@TK2MSFTN GP03.phx.gbl...

Hi All
>
I have a windows forms Application (SAM) in vb.net 2008 using .net
framework V2
>
One and only one customer out of 30 customers is getting errors daily
where they have to close and restart my application, sometimes several
times a day
>
The customer has XP Home SP2
>
The event viewer shows the following although not always in the same
sequence
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4 sam, P5
1.0.0.0, P6 48d969a4, P7 5, P8 0, P9 system.nullrefe renceexception, P10
NIL.
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4
microsoft.visua lbasic, P5 8.0.0.0, P6 471ee7ea, P7 86, P8 a2, P9
system.componen tmodel.win32, P10 NIL.
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48eea25c, P4
microsoft.visua lbasic, P5 8.0.0.0, P6 471ee7ea, P7 5e, P8 1e1, P9
34ssps20bdj3nj0 wmit5kamzhvglfz cc, P10 NIL.
>
Hanging application SAM.exe, version 1.0.0.0, hang module hungapp, version
0.0.0.0, hang address 0x00000000.
>
I am lost as to what may be causing it and like I said it only happens to
the 1 customer
>
Any ideas what it could be and any ideas on how to troubleshoot it further
to find the exact cause?
>
Regards
Steve
>
>
>

**Family Tree Mike** · Oct 16 '08, 10:45 PM

Re: System.NullRefe rence exception

Just a shot in the dark, but can the user run your app as the administrator
successfully? Often this can be caused by some assumption of full
permissions somewhere in code. Things like reading or writing registry keys
may work 9 out of 10 times (or 29 out of 30 in your case).

"Steve" <ga630sf@nospam .nospamwrote in message
news:%23YHSjo9L JHA.3504@TK2MSF TNGP02.phx.gbl. ..

Hi All
>
Thanks for the responses
>
I have try/catch blocks in most of my routines
>
I also have a code in MyApplication_U nhandledExcepti onroutine, which
doesn't fire (see below)
>
'writes unhandled exceptions to my log file
>
mymsgbox(e.Exce ption.Message & vbCr & e.Exception.Inn erException.ToS tring)
>
If e.Exception.Mes sage.Length 200 Then
>
savetolog("Auto ", e.Exception.Mes sage.Substring( 0, 199))
>
Else
>
savetolog("Auto ", e.Exception.Mes sage)
>
End If
>
The screen they get when the error occurs is not the usual .net screen
showing the error details, but the Microsoft screen with send report /
don't send buttons
>
Not sure if this makes a difference
>
Regards
>
Steve
>
>
>
>
>
"Steve" <ga630sf@nospam .nospamwrote in message
news:uwEjx13LJH A.1736@TK2MSFTN GP03.phx.gbl...

>Hi All
>>
>I have a windows forms Application (SAM) in vb.net 2008 using .net
>framework V2
>>
>One and only one customer out of 30 customers is getting errors daily
>where they have to close and restart my application, sometimes several
>times a day
>>
>The customer has XP Home SP2
>>
>The event viewer shows the following although not always in the same
>sequence
>>
>EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4 sam, P5
>1.0.0.0, P6 48d969a4, P7 5, P8 0, P9 system.nullrefe renceexception, P10
>NIL.
>>
>EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4
>microsoft.visu albasic, P5 8.0.0.0, P6 471ee7ea, P7 86, P8 a2, P9
>system.compone ntmodel.win32, P10 NIL.
>>
>EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48eea25c, P4
>microsoft.visu albasic, P5 8.0.0.0, P6 471ee7ea, P7 5e, P8 1e1, P9
>34ssps20bdj3nj 0wmit5kamzhvglf zcc, P10 NIL.
>>
>Hanging application SAM.exe, version 1.0.0.0, hang module hungapp,
>version 0.0.0.0, hang address 0x00000000.
>>
>I am lost as to what may be causing it and like I said it only happens to
>the 1 customer
>>
>Any ideas what it could be and any ideas on how to troubleshoot it
>further to find the exact cause?
>>
>Regards
>Steve
>>
>>
>>

>
>

**Jialiang Ge [MSFT]** · Oct 17 '08, 07:35 AM

Re: System.NullRefe rence exception

Hello Steve,

If an exception goes unhandled in a .NET 2.0 application, it will use
Windows Error Reporting to send a report automatically. Although we have
MyApplication_U nhandledExcepti onroutine in the application (according to
your code snippet, I think it¡¯s added through the
Application.Thr eadException event) and add try/catch in most of the
routines, there is actually another source of UnhandledExcept ion:

¡°AppDomain.Unh andledException ¡±

Application.Thr eadException is used to add the event handler for handling UI
thread exceptions. AppDomain.Unhan dledException adds the event handler for
handling non-UI thread exception. In other words, if an exception is thrown
from a non-UI thread, Application.Thr eadException is not able to capture it,
and it will go to the ¡°Windows Error Report¡± dialog. In addition, we need
to call
Application.Set UnhandledExcept ionMode(Unhandl edExceptionMode .CatchException );
to set the unhandled exception mode to force all windows form error to go
through our handler. A typical example is:

SecurityPermiss ion(SecurityAct ion.Demand, Flags =
SecurityPermiss ionFlag.Control AppDomain)]
public static void Main(string[] args)
{
// Add the event handler for handling UI thread exceptions to the event.
Application.Thr eadException += new
ThreadException EventHandler(Er rorHandlerForm. Form1_UIThreadE xception);

// Set the unhandled exception mode to force all Windows Forms errors to
go through
// our handler.
Application.Set UnhandledExcept ionMode(Unhandl edExceptionMode .CatchException );

// Add the event handler for handling non-UI thread exceptions to the
event.
AppDomain.Curre ntDomain.Unhand ledException +=
new
UnhandledExcept ionEventHandler (CurrentDomain_ UnhandledExcept ion);

// Runs the application.
Application.Run (new ErrorHandlerFor m());
}

private static void CurrentDomain_U nhandledExcepti on(object sender,
UnhandledExcept ionEventArgs e)
{
try
{
Exception ex = (Exception)e.Ex ceptionObject;
// dump the call stack here

// Create an EventLog instance and assign its source.
EventLog myLog = new EventLog();
myLog.Source = "ThreadExceptio n";
myLog.WriteEntr y(errorMsg + ex.Message + "\n\nStack Trace:\n" +
ex.StackTrace);
}
catch (Exception exc)
{
try
{
MessageBox.Show ("Fatal Non-UI Error",
"Fatal Non-UI Error. Could not write the error to the event
log. Reason: "
+ exc.Message, MessageBoxButto ns.OK, MessageBoxIcon. Stop);
}
finally
{
Application.Exi t();
}
}
}

(See MSDN article:
http://msdn.microsoft.com/en-us/libr...ptionmode.aspx)

With the above code, we can dump the call stack of the unhandled exception
in the exception handler, and see how the exception is thrown.

Regards,
Jialiang Ge (jialge@online. microsoft.com, remove ¡®online.¡¯)
Microsoft Online Community Support

Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
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"Steve" <ga630sf@nospam .nospamwrote in message
news:uwEjx13LJH A.1736@TK2MSFTN GP03.phx.gbl...

Hi All
>
I have a windows forms Application (SAM) in vb.net 2008 using .net
framework V2
>
One and only one customer out of 30 customers is getting errors daily
where they have to close and restart my application, sometimes several
times a day
>
The customer has XP Home SP2
>
The event viewer shows the following although not always in the same
sequence
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4 sam, P5
1.0.0.0, P6 48d969a4, P7 5, P8 0, P9 system.nullrefe renceexception, P10
NIL.
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48d969a4, P4
microsoft.visua lbasic, P5 8.0.0.0, P6 471ee7ea, P7 86, P8 a2, P9
system.componen tmodel.win32, P10 NIL.
>
EventType clr20r3, P1 sam.exe, P2 1.0.0.0, P3 48eea25c, P4
microsoft.visua lbasic, P5 8.0.0.0, P6 471ee7ea, P7 5e, P8 1e1, P9
34ssps20bdj3nj0 wmit5kamzhvglfz cc, P10 NIL.
>
Hanging application SAM.exe, version 1.0.0.0, hang module hungapp, version
0.0.0.0, hang address 0x00000000.
>
I am lost as to what may be causing it and like I said it only happens to
the 1 customer
>
Any ideas what it could be and any ideas on how to troubleshoot it further
to find the exact cause?
>
Regards
Steve
>
>
>

System.NullReference exception

System.NullReference exception

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