What things should I consider when I get an intermittent exception in Visual Basic .net (debugging in Visual Studio Express 2010)? - vb.net

Question

I'm testing my Visual Basic .net application by running it in Visual Studio express.
Sometimes it runs OK, but other times I get an exception (details below, if useful). I'm not sure why I get the exception as the particular part of the application that I am testing re-uses code that works OK for other features.
What should I check, what would give me a hint as to the root cause.
Things I tried so far are:
Rewriting some of the code to be more robust. The outcome of this was that this approach was getting out of control - I was correcting everything. I made changes such asing alternative libraries (e.g. replacing CInt with convertTo etc). Some lazy declarations, but it occurred to me that there was no problem with these with the code before my changes. And every change I seemed to solve uncovered yet another problem, another different exception
So I thought something must be fundamentally wrong with my installation, and a search found discussion group posts from people experiencing something similar. The suggested remedy would be to re-install the .net framework. So I did that and the problems still occured.
Any thoughts on approach to get to the root of the problem? I'm not asking for a solution but some fresh ideas would be very welcome.
Update:
I've added in the following code to get more detail (+1 thanks #Meta-Knight)
Dim exceptionMessage As String = ex.Message
Console.WriteLine("Message: \n" & exceptionMessage)
Dim exceptionTargetSite As String = ex.TargetSite.ToString
Console.WriteLine("Inner: \n" & ex.TargetSite.ToString)
Dim exceptionSource As String = ex.Source
Console.WriteLine("Source\n:" & exceptionSource)
' put the stack trace into a variable
' (this helps debugging - put a break point after this is assigned
' to see the contents)
Dim stackTrace As String = ex.StackTrace.ToString()
Console.WriteLine("Stack trace\n:" & stackTrace)
More details about exception
Error - Exception Message
"Arithmetic operation resulted in an overflow."
Exception Target Site:
"Int32 ToInteger(System.String)"
Exception Source:
"Microsoft.VisualBasic"
at Microsoft.VisualBasic.CompilerServices.Conversions.ToInteger(String Value) at MyCo_3rd-Party-Industrial-Printing-System.Customer_EanUpc_serialNumberGeneratorAssembly.btnPrint_Click(Object sender, EventArgs e) in C:\labelprint\MyCo 3rd-Party-Industrial-Printing-System v2\MyCo 3rd-Party-Industrial-Printing-System\PrintForms\Customer_EanUpc_serialNumberGeneratorAssembly.vb:line 271 at System.Windows.Forms.Control.OnClick(EventArgs e) at System.Windows.Forms.Button.OnClick(EventArgs e) at System.Windows.Forms.Button.PerformClick() at System.Windows.Forms.Form.ProcessDialogKey(Keys keyData) at System.Windows.Forms.Control.ProcessDialogKey(Keys keyData) at System.Windows.Forms.Control.PreProcessMessage(Message& msg) at System.Windows.Forms.Control.PreProcessControlMessageInternal(Control target, Message& msg) at System.Windows.Forms.Application.ThreadContext.PreTranslateMessage(MSG& msg) at System.Windows.Forms.Application.ThreadContext.System.Windows.Forms.UnsafeNativeMethods.IMsoComponent.FPreTranslateMessage(MSG& msg) at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData) at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.RunDialog(Form form) at System.Windows.Forms.Form.ShowDialog(IWin32Window owner) at System.Windows.Forms.Form.ShowDialog() at MyCo_3rd-Party-Industrial-Printing-System.utlForm.openNewModalForm(String form) in C:\labelprint\MyCo 3rd-Party-Industrial-Printing-System v2\MyCo 3rd-Party-Industrial-Printing-System\Utilities\utlForm.vb:line 128
Update 2:
The code around line 272 was:
For i As Integer = 1 To CInt(numQuantity)
If generationMethods() Then
The code around line 272 is now (I've adjusted it):
Dim numQuantityAsStr As String = numQuantity.Text
Dim numQuantityAsInt As Integer = Convert.ToInt32(numQuantityAsStr)
For i As Integer = 1 To numQuantityAsInt
If generationMethods() Then
numQuantity is a String variable for a field in the Windows form I am using and this has a value put in it by the user, the field is used to specify the quantity of something so this variable is converted to a integer so that it can be used in a for loop. The test value I am using is always entering 1 in this field, and sometimes this causes the exception.
My alteration uses what I think is a more modern type conversion Convert.ToInt32 rather than CInt I've also introduced intermediate steps to help debug.
The exception now does not occur here but I did try this the other week and another separate exception popped up (if I remember) from somewhere else so we'll see if this fixes it. Any thoughts as to why using a different conversion utility would solve the problem?
Update 3:
An Exception now occurs elsewhere:
(But why?! This one is thrown from library code!)
The following code caused it:
Dim dateNowAsStr As String = DateTime.Now.Date.ToString
Exception Message:
"Value to add was out of range. Parameter name: value"
Exception target site:
"System.DateTime Add(Double, Int32)"
Exception source:
"mscorlib"
" at System.DateTime.Add(Double value, Int32 scale) at System.TimeZoneInfo.TransitionTimeToDateTime(Int32 year, TransitionTime transitionTime) at System.TimeZoneInfo.GetDaylightTime(Int32 year, AdjustmentRule rule) at System.TimeZoneInfo.GetIsDaylightSavingsFromUtc(DateTime time, Int32 Year, TimeSpan utc, AdjustmentRule rule, Boolean& isAmbiguousLocalDst) at System.TimeZoneInfo.GetDateTimeNowUtcOffsetFromUtc(DateTime time, Boolean& isAmbiguousLocalDst) at System.DateTime.get_Now() at GenerationLibrary.GenerationUtilities.callserialNumberGenerator(String serialNumberGeneratorSnFile, String serialNumberGeneratorRange, DefaultSettingsHandler settings) in C:\labelprint\MyCo 3rd-Party-Industrial-Printing-System v2\GenerationLibrary\GenerationUtilities.vb:line 28 at GenerationLibrary.MyCoSnGeneration.constructMyCoSn(DataRow& oDataRow, DefaultSettingsHandler& settings) in C:\labelprint\MyCo 3rd-Party-Industrial-Printing-System v2\GenerationLibrary\MyCoSnGeneration.vb:line 18 at MyCo_3rd-Party-Industrial-Printing-System.Customer_EanUpc_serialNumberGeneratorAssembly.generationMethods() in C:\labelprint\MyCo 3rd-Party-Industrial-Printing-System v2\MyCo 3rd-Party-Industrial-Printing-System\PrintForms\Customer_EanUpc_serialNumberGeneratorAssembly.vb:line 40 at MyCo_3rd-Party-Industrial-Printing-System.Customer_EanUpc_serialNumberGeneratorAssembly.btnPrint_Click(Object sender, EventArgs e) in C:\labelprint\MyCo 3rd-Party-Industrial-Printing-System v2\MyCo 3rd-Party-Industrial-Printing-System\PrintForms\Customer_EanUpc_serialNumberGeneratorAssembly.vb:line 275 at System.Windows.Forms.Control.OnClick(EventArgs e) at System.Windows.Forms.Button.OnClick(EventArgs e) at System.Windows.Forms.Button.PerformClick() at System.Windows.Forms.Form.ProcessDialogKey(Keys keyData) at System.Windows.Forms.Control.ProcessDialogKey(Keys keyData) at System.Windows.Forms.Control.PreProcessMessage(Message& msg) at System.Windows.Forms.Control.PreProcessControlMessageInternal(Control target, Message& msg) at System.Windows.Forms.Application.ThreadContext.PreTranslateMessage(MSG& msg) at System.Windows.Forms.Application.ThreadContext.System.Windows.Forms.UnsafeNativeMethods.IMsoComponent.FPreTranslateMessage(MSG& msg) at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData) at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.RunDialog(Form form) at System.Windows.Forms.Form.ShowDialog(IWin32Window owner) at System.Windows.Forms.Form.ShowDialog() at MyCo_3rd-Party-Industrial-Printing-System.utlForm.openNewModalForm(String form) in C:\labelprint\MyCo 3rd-Party-Industrial-Printing-System v2\MyCo 3rd-Party-Industrial-Printing-System\Utilities\utlForm.vb:line 128"
Update 4
BUT
Dim dateNowAsStr As String = CStr(DateTime.Now)
does not cause the exception

Answer 1

Before rewriting or reinstalling anything, you should try to identify the source and the reason for the error.
The first thing to do is to analyse the error message and stack trace. If you include debugging files (.pdb) with your application's files, you will get more detailed information such as the line number which can be helpful.
If that doesn't give enough information about the circumstances of the error, then you can add some logging to your app. By logging what the user does in your app it might help reproduce the problem.
Finally you can always get help by searching on google or asking on StackOverflow, but make sure to include the actual error message, not just the stack trace... You should also post the code where the error happens.
Edit:
So the actual error is: "Arithmetic operation resulted in an overflow."
Googling this would have helped: you would have found out that such an error happens when you're trying to convert a number which is out of bounds for an integer. If you expect to have some very large numbers you can try converting to Long instead.

Answer 2

I think you can start by looking at what is at line 271 of the Customer_EanUpc_serialNumberGeneratorAssembly.vb source code file.
Which is located: C:\labelprint\MyCo 3rd-Party-Industrial-Printing-System v2\MyCo 3rd-Party-Industrial-Printing-System\PrintForms\ directory.
It looks like the problem is related to a conversion between string to integer where maybe it failed because the string cannot be converted to integer... maybe it has alphanumeric characters...
"Microsoft.VisualBasic.CompilerServices.Conversions.ToInteger(String Value)"
Did you already check that?
Why you get the error some times and not always could be because (and I'm guessing here) the code in serialNumberGeneratorAssembly sometimes generates numeric only values (that can be correctly converted to integer) and some other times generates alphanumeric serial numbers (that throw the convertion exception).
UPDATE: the code that generates the Serial Numbers is generating numbers bigger than an Integer value. Try converting to Long instead of Integer... or have a look at System.Numerics.BigInteger in case those numbers are too big.
That explains the: "Arithmetic operation resulted in an overflow." exception message.