I have a few VB.NET programs to maintain, that have been ported from VB6 and use the old style Unstructured Exception Handling:
On Error GoTo yyy
My question is, can I still get a stack trace while using Unstructured Exception Handling, or do I have to convert them all to Structured Exception Handling (Try/Catch) in order to catch an exception with its full stack trace.
Here's a way to get the stack trace to the line that caused the exception, unlike the other answer which just traces to the routine where your error handler is. The error might have occurred in a different routine.
In the unstructured error handlers, just use the GetException property of the Err object to access the underlying exception - then use the StackTrace property. Like this:
Public Class Form1
Public Sub New()
' This call is required by the Windows Form Designer.'
InitializeComponent()
' Add any initialization after the InitializeComponent() call.'
On Error GoTo ErrHandle
Call test()
Exit Sub
ErrHandle:
MsgBox("Stack trace " & Err.GetException.StackTrace)
Exit Sub
End Sub
Private Sub test()
Call test2()
End Sub
Private Sub test2()
Dim d(2) As Double
MsgBox(d(-1))
End Sub
End Class
As you know yourself, all things being equal, one should always use structured exception handling. However, if you can't, you can get your own stack trace by using the StackTrace class.
NB: Calls to stack trace are expensive, and should only be used in - ahem - 'exceptional' circumstances.
e.g
MethodName = (New StackFrame(0)).GetMethod.Name ' Get the current method
MethodName = (New StackFrame(1)).GetMethod.Name ' Get the Previous method
MethodName = (New StackFrame(2)).GetMethod.Name ' Get the method before that
Related
I have another issue:
I am able to build my VB.NET application. However, when I go to debug it, I get an unhandled exception:
System.InvalidOperationException occurred HResult=0x80131509
Message=An error occurred creating the form. See
Exception.InnerException for details. The error is: Object reference
not set to an instance of an object. Source=ProovePC StackTrace:
at ProovePC.My.MyProject.MyForms.Create__Instance__[T](T Instance) in
:line 190 at ProovePC.My.MyProject.MyForms.get_Front1() at
ProovePC.My.MyApplication.OnCreateMainForm() in
C:\Users\Phillip\source\Workspaces\Upwork
Projects\ProoveIt\ProovePC\My Project\Application.Designer.vb:line 35
at
Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
at
Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()
at
Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[]
commandLine) at ProovePC.My.MyApplication.Main(String[] Args) in
:line 81
Inner Exception 1: NullReferenceException: Object reference not set to
an instance of an object.
The odd part is that it occurs in auto-generated code, in the Application.Designer.vb file. I have confirmed that the constructor is public and that the name of the form matches the name within this file:
Namespace My
'NOTE: This file is auto-generated; do not modify it directly. To make changes,
' or if you encounter build errors in this file, go to the Project Designer
' (go to Project Properties or double-click the My Project node in
' Solution Explorer), and make changes on the Application tab.
'
Partial Friend Class MyApplication
<Global.System.Diagnostics.DebuggerStepThroughAttribute()> _
Public Sub New()
MyBase.New(Global.Microsoft.VisualBasic.ApplicationServices.AuthenticationMode.Windows)
Me.IsSingleInstance = true
Me.EnableVisualStyles = true
Me.SaveMySettingsOnExit = true
Me.ShutDownStyle = Global.Microsoft.VisualBasic.ApplicationServices.ShutdownMode.AfterAllFormsClose
End Sub
<Global.System.Diagnostics.DebuggerStepThroughAttribute()> _
Protected Overrides Sub OnCreateMainForm()
Me.MainForm = Global.ProovePC.Front1 'Error occurs here?
End Sub
End Class
End Namespace
I am a little lost on this since I am new VB.NET, but I would like to think that the fix is a simple one. For those wondering, I am running visual studio 2017. I should note that I come from a C# background and recently got into vb.net. So please, explain as much as possible.
Edit:
Form Constructor:
Public Sub New()
' This call is required by the designer.
'NewMethod()
InitializeComponents()
' Add any initialization after the InitializeComponent() call.
End Sub
Edit:
Ok so here is the interesting part, now I am getting the error on the InitializeComponents function itself within the auto generated constructor of the form. Once I comment this function out, I am able to build and run the application. I only get so far because that application needs hardware to fully run which I have not connected yet.
Now, here is the interesting part, if I were to comment out the constructor, there is a line above it that comes back as undefined reference error:
Public MainStatus As StatusStrip = StatusStrip1 'Error is here now
'Public Sub New()
' This call is required by the designer.
'InitializeComponent()
' Add any initialization after the InitializeComponent() call.
'End Sub
For those wondering, I am now in the front1.vb file
there was a property within the form control that was being set to nothing when it needs to be set to Me.
As for the random line of code, Public MainStatus As StatusStrip = StatusStrip1 I think that it was accidentally copy pasted there as the variable is only used at that line. I commented it out and everything builds good now.
I have another question considering events and exceptions
A small introduction to my project: I'm working in a 3 layer architecture, so I have a GUI(form), BLL(Business logic layer) and a DAL(data acces layer).
So my GUI is linked to a BLL which is connected to several DAL classes. For example my BLL has a class clsCSV (which reads and writes CSV files)
I now want to raise events and/or catch exceptions from this class to inform the user and log exceptions. There are 3 events: "ErrorLoad", "ErrorWrite", "Ready"
Public Class clsCSV
Public Sub New()
End Sub
Public Function Load(sFilePath As String)
Dim oFileHelper As New DelimitedFileEngine(Of clsItem)
Dim oList As New List(Of clsItem)
' Load a CSV file
Try
oList = oFileHelper.ReadFileAsList(sFilePath)
Catch ex As Exception
'RaiseEvent ErrorLoad("")
clsErrorLog.Log(ex)
Finally
End Try
' If the list is empty return nothing
If Not IsNothing(oList) Then
Return oList
Else
Return Nothing
End If
End Function
Public Sub Write(sFilePath As String, oList As List(Of clsTranslatedItem))
Dim oFileHelper As New DelimitedFileEngine(Of clsTranslatedItem)
oFileHelper.WriteFile(sFilePath, oList)
RaiseEvent Ready()
End Sub
Public Event ErrorLoad(ByVal sender As Object, ByVal e As EventArgs)
Public Event ErrorWrite(sMessage As String)
Public Event Ready()
End Class
There is a try-catch in my public sub load which catches any exception and logs it to a text file by calling clsErrorLog.log(ex) which then calls this class and logs the error:
Public Shared Sub Log(ex As Exception)
Try
Dim oBestand As New System.IO.StreamWriter(My.Computer.FileSystem.SpecialDirectories.Desktop & "\ErrorLog.txt", True)
If Not IsNothing(oBestand) Then
oBestand.WriteLine("")
oBestand.WriteLine(My.Computer.Clock.LocalTime.ToString)
oBestand.WriteLine(ex.Message)
oBestand.WriteLine(ex.StackTrace)
oBestand.WriteLine("_________________________________________")
oBestand.Close()
End If
Catch exc As Exception
End Try
End Sub
This works fine, but now I want to inform the user that an error occured, so I was thinking to raise an event called "ErrorLoad" (in clsCSV) and catch this in my BLL. But what can I do then? Add a sub that handles this event, which then raises an event in the BLL, caught by the GUI? or is this a long way to this?
I also want to do this for the other events offcourse. But the whole event system in the layered architecture is a bit confusing.
Anyone who can enlighten me?
Thanks in advance!
Without knowing the implementation details of your UI, I can only give you some general advice.
You need some kind of two directional communication between your GUI and your BLL. For example in WPF this is usually done using INotifyPropertyChanged interface and the event it defines.
So the BLL raises a event and the GUI is listening. The basically only has the task of informing the GUI that it has to check a specific property or function or anything like this from the BLL. The rest is up to the GUI to do so and inform the user.
I wouldn't do that using exceptions. These are there to handle the error path of specific functions. This path is done once your BLL noticed the error and prepared it for the UI handling.
I am using VS2012 VB.net.
Can I please have some help in creating some code to calculate the error line of an exception and also the function that the exception occurred in.
Here is my current code:
Partial Friend Class MyApplication
Public exceptionListOfExceptionsToNotPauseOn As New List(Of ApplicationServices.UnhandledExceptionEventArgs)
Private Sub MyApplication_UnhandledException(sender As Object, e As ApplicationServices.UnhandledExceptionEventArgs) Handles Me.UnhandledException
Dim msgboxResult As MsgBoxResult
Dim booleanExceptionFoundInList As Boolean = False
'Dim trace As System.Diagnostics.StackTrace = New System.Diagnostics.StackTrace(ex, True)
'Dim exceptionLineNumber = trace.GetFrame(0).GetFileLineNumber()
For x = 0 To exceptionListOfExceptionsToNotPauseOn.Count - 1
If exceptionListOfExceptionsToNotPauseOn(x).Exception.Message = e.Exception.Message Then
booleanExceptionFoundInList = True
End If
Next
If Not booleanExceptionFoundInList Then
msgboxResult = MessageBox.Show("An exception error has occured." & vbCrLf & "Error message: " & e.Exception.Message & vbCrLf & "Do you wish to pause on this exception again?", "Exception", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Question)
If msgboxResult = Microsoft.VisualBasic.MsgBoxResult.No Then
exceptionListOfExceptionsToNotPauseOn.Add(e)
End If
End If
e.ExitApplication = False
End Sub
End Class
UPDATE
The code for the trace code uses an Exception data type where as the code for handling unHandled exceptions above has a parameter of "e As ApplicationServices.UnhandledExceptionEventArgs". Can I use the trace code with this data type? Do I need to cast it to an exception type? Or is it not possible?
I am not mastering in Vb.Net but previously i used below code, may be it can help you
[ex.StackTrace()]
Try
'Your Code goes here
Catch ex As Exception
MsgBox(ex.StackTrace())
End Try
Here are a couple of tips. First is to use PostSharp its a AOP kit that will let you trace all methods entry and exit using Attributes. This would direct you to the function straight away.
Another trick. Subscribing to the ThreadExceptionEventHandler actually does cause the debugger to break on unhandled exceptions! Hence temporarily comment out your MyApplication_UnhandledException and add a ThreadExceptionEventHandler
<STAThread> _
Public Shared Sub Main(args As String())
Try
'your program entry point
Application.ThreadException += New ThreadExceptionEventHandler(Application_ThreadException)
'manage also these exceptions
Catch ex As Exception
End Try
End Sub
Private Sub Application_ThreadException(sender As Object, e As ThreadExceptionEventArgs)
ProcessException(e.Exception)
End Sub
Another trick is is not to run under the debugger. The debugger is masking the exception for some reason. If you run your app normally (Ctrl+F5), you'll get the usual Unhandled exception has occurred in your application... Continue/Quit? dialog.
The code for handling unHandled exceptions above has a parameter of "e
As ApplicationServices.UnhandledExceptionEventArgs". Can I use the
trace code with this data type?
No.
You cannot easily use your trace code datatype with the UnhandledExceptionEventArgs. One idea might be to make a class that inherits from UnhandledExceptionEventArgs but I don't know how you'd call the MyApplication_UnhandledException function with the special type, because that function is invoked when an Exception is Unhandled.
I'm developing an application with an error log when something goes bad. It must send an e-mail with the error details so I can remotely fix and upload a new update with the fix.
I'm using Try Catch Exception but I have a lot of methods to include this option in.
Is there another way to do it without doing so much code?
Since exceptions bubble up to the application instance try using the Application.SetUnhandledExceptionMode Method.
From above MSDN Link:
It is often not feasible to catch all of the exceptions thrown by
Windows Forms. Using this method, you can instruct your application
whether it should catch all unhandled exceptions thrown by Windows
Forms components and continue operating, or whether it should expose
them to the user and halt execution.
Public Shared Sub Main()
' Add the event handler for handling UI thread exceptions to the event.
AddHandler Application.ThreadException, AddressOf Form1_UIThreadException
' Set the unhandled exception mode to force all Windows Forms errors to go through
' our handler.
Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException)
' Add the event handler for handling non-UI thread exceptions to the event.
AddHandler AppDomain.CurrentDomain.UnhandledException, AddressOf CurrentDomain_UnhandledException
' Runs the application.
Application.Run(New Form1()) '' This is your applications Main Form
End Sub
Private Shared Sub Form1_UIThreadException(ByVal sender As Object, ByVal t As ThreadExceptionEventArgs)
'Put Error Handling Code here see the MSDN article for an example implementation
End Sub
Private Shared Sub CurrentDomain_UnhandledException(ByVal sender As Object, _
ByVal e As UnhandledExceptionEventArgs)
''Put Error Handling Code here see the MSDN article for an example implementation
End Sub
Sorry, misunderstood your question. Try putting your logic in a method and just try to call that method in every try catch statement you have.
Example:
Public Shared Sub Method1()
Try
'Method logic here
Catch ex As Exception
EmailError(ex)
End Try
End Sub
Public Shared Sub EmailError(ex As Exception)
'your remote error email logic here
End Sub
My goal here is to get stack trace information from a dynamically loaded assembly. If the dynamically loaded assembly just throws the error back to the caller, the stack trace information doesn’t tell you the location in the dynamic assembly where the error occurred. If I throw my own exception, passing in the original exception, it will get added as an inner exception and will have the information need. I’m trying to avoid changing all my dynamic assemblies to throw new exceptions. Does anybody know a better way to get the stack trace information from a dynamically loaded assembly?
Public Class ErrorPlugin
' Example Function from plug in DLL
Public Function SimpleExample() As Double
Dim RentedUnits As Double = 42
Dim NumberUnits As Double = 0
Try
' Just need to generate exception
Return RentedUnits \ NumberUnits
Catch ex As Exception
' Give's me no Stack Trace infomation.
'Throw
' This will give me Stack Trace infomation,
' but requires adjusting all the plugins.
Throw New Exception("Stop dividing by zero.", ex)
End Try
End Function
End Class
Imports System.Reflection
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim rpt As Object
Dim r As Double
Try
rpt = LoadReport("C:\ErrorPlugin\bin\Debug\ErrorPlugin.dll")
r = rpt.SimpleExample()
Catch ex As Exception
MsgBox(ex.Message & vbCrLf & ex.StackTrace)
If ex.InnerException IsNot Nothing Then
MsgBox(ex.InnerException.StackTrace)
End If
End Try
End Sub
Public Function LoadReport(ByVal FileName As String) As Object
Dim m_ReportAssembly As [Assembly]
Dim m_ReportClass As Type
Dim rpt As Object
Try
m_ReportAssembly = Assembly.LoadFrom(FileName)
For Each m_ReportClass In m_ReportAssembly.GetTypes
If m_ReportClass.Name.ToLower = "ErrorPlugin".ToLower Then
rpt = Activator.CreateInstance(m_ReportClass)
Exit For
End If
Next
Return rpt
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Function
End Class
Can you see what happens if you just Throw, not Throw ex? From memory, "throw ex" does a copy while "throw" actually rethrows the caught exception. I guess your "throw ex" is effectively resetting the stack trace to your local code.
MSDN says if you're rethrowing exceptions you should add value to it by wrapping it in a new exception, otherwise you might as well not bother with try/catch in your example.
Do you have the debug symbols for these external DLL's? If you look at the stack trace, and it reads "External Code", that should be expanded into the DLL stack if you have the DLL debug symbols loaded while debugging, since the symbols will provide your debugger with the necessary info to walk the stack.
Either do this by manually loading the symbols, via the Modules Window in the Debug menu, or running against a debug build of the DLL.