Catching NullReferenceException?
Apr 5, 2011
When I debug a program my IDE simply does not catch System.NullReferenceException - execution continues as if there were nothing wrong.Moreover, when I go to the menu Debug/Exceptions System.NullReferenceException is not even in the list(Common Language Runtime Exceptions).
I manually add it (there is the Add button) and I put a checkmark in the 'Thrown' and 'User unhandled' column - now IDE catches it, but after I re-load the project the situation re-appears - and NullReferenceException is not on the list again. What may be wrong?
Update:No, when I step through the code the execution does not continue but exits the current block of code (sub or function). There were no Try...Catch blocks and there is a message: A System.NullReferenceException occured in MSCorlib.dll... But why doesn't the debugger stop at this line?
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Mar 14, 2011
I am trying to catch an exception but occasionally get an inner exception. I want to output both into a label. I often get Object reference not set to instance of an object if there is no inner exception.
Catch ex As Exception
exError = ex.Message.ToString
If Not ex.InnerException.Message Is Nothing Then
[Code]....
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Aug 8, 2011
I have a simple function which tries to get a value from an Obout grid filter column, and if the value is empty, ignores it and moves on. For some reason this code ignore my catch block and always shows a System.FormatException when the input string is empty More bizarre, if I use visual studio's debugger and set a breakpoint on that line, the catch block functions normally (after I continue from that line). I have already confirmed that my Debug | Exceptions | CLR are not set to catch when thrown. I have also confirmed this same behavior in the production version.
[Code]...
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May 8, 2009
I have 5 errors that come up every time I run my project They are all "A first chance exception of type 'System.ArgumentException' occurred in System.Drawing.dll"
I have try catch blocks around every piece of code I have written, and it does not seem to catch them, so I opted to catch the appdomain.UnHandledException.
That does not seem to catch them either If I step through the code line by line (several hundred lines so I hold down f8) it does not make the error...
Only when I run full speed.
I can only figure that I am accessing something maybe before an object is completely drawn, however how in the heck would anyone suggest I go about finding it, and why will my global event handler not catch them?
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Dec 22, 2009
I am using BackgroundWorker to connect asynchronously to a database. Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
[Code]...
While my connection is being opened, I have a "Loading" animation show in a lblCalibration. Once it's connected, the animation stops successfully and shows the calibrated record that I am fetching from my db.
However, if there is an error while connecting to my db for any reason, it does not work. My app freezes. The reason is because I am trying to make a cross-thread call while trying to Catch the error in the DoWork event.[URL]..
but still cannot seem to make any progress. Does anyone have any tips or advice on how to properly catch the error and still run BackgroundWorker?
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Feb 24, 2012
Take the TripPriceService.wsdl from this link Add a service reference(ServiceReference1) to a windows application, by giving the wsdl from the mentioned wsdl file saved in local folder. My question has two parts
1) Is the below fault message a valid soap fault as per the wsdl(TripPriceServiceException)?
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:trip="http://trip.price.service">
<soapenv:Header/>
<soapenv:Body>
[code]....
2)Now How to handle and catch the detail tag, when the response is a soap:fault?
Imports windowsapp1.ServiceReference1
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim obj As New ServiceReference1.TripPriceServiceFacadeClient
[code]....
The line obj.getTripPrice, invokes the service. However will it throw an exception if the response is a soap fault(of type TripPriceServiceException)? How to handle such cases, do we need to use ServiceReference1.TripPriceServiceException? We are in a need to handle such faults in our webservice client.
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Feb 18, 2012
Private _pages As New List(Of Panel)
Public ReadOnly Property pages() As List(Of Panel)
Get
[code].....
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Apr 5, 2011
I have read the documentation on RaiseEvent and Even but still confused. I am using a class that i call that performs a task on a thread.
vb
Public Property MyVar As String
Public Sub MuSub()
[code]....
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Sep 16, 2009
'SHEETS For Each ctrl As Control In Me.Controls What am I doing wrong here? When I put in manual text after the line return it fill in but as is it doesn't pick up all the checkboxes under HEADINGS. It does create all the sheets under SHEETS.
Code:
If (TypeOf ctrl Is CheckBox AndAlso CType(ctrl, CheckBox).Checked) AndAlso CType(ctrl, CheckBox).Name.Contains("Sheet") Then
wb.Worksheets("Template").copy(after:=sheet)
[Code]....
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Apr 1, 2010
I'm not even sure if that's what I want.But, here's my question. I have written a small program to automate the running of some files. These files have the potential to give an error in the form of a MessageBox which will halt the whole process. Is there a way to detect if that window pops up so that I can kill the process so the next file can run.
Also, if I can get the location of this MessageBox, is it possible to get text out of it so that maybe I can email myself the error so that the processes can keep running but I cango to that file and fix it.
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Apr 25, 2012
I put a try/catch block around a bit of code that occasionaly throws an expected exception, but rather than catching it and displaying the message box, it stops the debugger and alerts me that the exception is unhandled.How do I handle this exception so my code doesn't stop when the exception occurs?
Friend myDevInfo As New devInfo
''' <summary>
''' Closes the device handle obtained with CreateFile and frees resources.
[code]....
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Feb 5, 2011
I have a VB.NET application (VS2010, .NET 4.0) that seems to throw an exception under some unknown conditions after a number of hours. In addition to the main thread, there are additional threads running. In reading this link: [URL] it seems like this would be a big help in trapping this exception. I have what are probably some very basic questions:
1. I assume ErrorHandlerForm() in the example refers to the main form of the application, setup.vb in my case. Therefore the last line in the example should be:
[Code]...
I would have expected to to replace ErrorHandlerForm.Form1_UIThreadException with find a setup event such as Setup_UIThreadException but there doesn't appear to be sucn an event.
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May 5, 2011
While I understand ApplicationEvents.vb won't catch exceptions in another thread, is there any reason why it shouldn't catch exceptions in the UI thread? From time to time I get exceptions that simply crash the program, even though an exception handler is defined as follows:
Private Sub MyApplication_UnhandledException(ByVal sender As Object, ByVal e As Microsoft.VisualBasic.ApplicationServices.UnhandledExceptionEventArgs) Handles Me.UnhandledException
[code].....
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Jun 30, 2011
I have a simple form with one text box that pass data to SQL and I want it to submit when the user hits the enter key.
In Firefox, this works great. The user puts a number hits enter gets back the results.
However in IE 8 and IE 9 this is not working.
<form id="form1" runat="server" accept="cmdclick"
style="background-position: center; background-image: url('BG.gif'); background-repeat: no-repeat;">
[Code]....
I am not sure what would cause this. I see a lot of people using JavaScript to go around the problem however I do not know how to write JavaScript code.
How can this be done (preferably without JavaScript)?
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May 9, 2012
I made a application in VB.Net. But some users face crash upon startup. That is "A problem caused this program from working correctly" with just one button "Close the program". Since there are lot of things happening when the app loads
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Jul 22, 2009
I have an ArrayList that is populated with Objects. These Objects raise events at certain times. How can I capture these events from the ArrayList? i.e.
I want something like this:
Public Sub MyRaisedEvent(ByVal obj as MyObject) Handles MyArrayList.MyEvent
End Sub
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Nov 10, 2010
I have a method as follows:
Public Sub Send()
Dim caughtException As Exception = Nothing
Try
//Attempt action.
Catch ex As Exception //Custom exceptions which can be thrown all inherit from Exception.
//Instantiate error object to be logged.
caughtException = ex
End Try
//Log action and if there is an error log this too.
If caughtException IsNot Nothing Then Throw caughtException
End Sub
It is essential that I log the error for reports, which after research, rethrowing the exception is the right thing to do. What I am concerned about is preservation of stack information. In order to keep the code DRY I am logging the action in one place - after the exception has been caught. This functionality is ultimately exposed via WCF.
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Mar 9, 2011
How do i catch an exception for the following piece of code?
If File.Exists(Path)Then
m_TempTable.ReadXml(Path,XmlReadMode.ReadSchema)
I deliberately deleted some code from the xml file to replicate a corrupt file but cannot catch the exception before the program trips up. I want to be able to notify the user there is a corrupt file and get them to re-install it.I have tried trying and catching but the debugger always stops with an XmlSchemaException at - m_TempTable.ReadXml(Path,XmlReadMode.ReadSchema)
The xml file is static information that needs no changing or saving. Would another way of storing this info be better?
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Mar 14, 2011
I have a VB.NET winforms solution, and would like to add the standard application exception handlers - Application.ThreadException and AppDomain.CurrentDomain.UnhandledException.I have the following code from MSDN
' Starts the application. '
<SecurityPermission(SecurityAction.Demand, Flags:=SecurityPermissionFlag.ControlAppDomain)> _
Public Shared Sub Main()
' Add the event handler for handling UI thread exceptions to the event. '
[code]....
How can I do it in VB.NET when I have no acces to the Sub Main() method?Is the case when "Enable Application Framework" of my solution properties is enabled (Sub Main is hidden)...
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Apr 13, 2011
I run a program multiplying decimals with integers. If a user enters a non 0 number etc. the try catch works its charm. i added some lines to clear the text boxes and that works fine but
lblReva.text = ""
does not clear the labels where the answers are displayed, on the contrary it displays the correct value calculated and enters a 0 for the erroneous entry. I would like to clear all the labels and text boxes(except the instruction and assingment labels)so the form is clean once more so the user can try to be "more on" target next time.
Try
decReva = CDec(txtBoxa.Text)
decRevb = CDec(txtBoxb.Text)
[code]....
Not integers but constants declared as decimals but that is immaterial here. "Doh"
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Mar 7, 2009
I'm trying to improve my app with some error catching. I have a module that downloads a file from the Internet to a local folder. At the moment, if the local folder doesn't exist, it just crashes here:
strLocalFile = New FileStream(pPath, FileMode.Create, FileAccess.Write, FileShare.None)
with error:
System.IO.DirectoryNotFoundException was unhandled
Message="Could not find a part of the path 'C:Documents and SettingsSimonDesktop estdownload.zip'."
Source="mscorlib"
How can I do something with that error and stop my app from crashing? Ideally, have a messagebox show saying 'directory not found' or similar.
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Sep 28, 2009
I'm just curious as to which one of these 3 error syntaxes in the try/catch is right.
vb.net
try
Catch ex As Exception
MessageBox.Show(ex.Message.ToString())
MessageBox.Show(ex.Message)
[Code]...
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Jan 23, 2009
Is it possible to catch windows messages when the application isnt in focus ?, its not for anything in particular, I have just been playing with wndproc and was just wondering
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Aug 16, 2011
I am using a TableAdapter to connect to my database table.When I perform an Update and someone else has updated the same row I get a concurrency violation error. As expected.So at this point I give the user the option to Save regardless or Cancel changesIf they cancel I can just performs a Fill to get an updated copy of the data but what if they want to overwrite? How do I actually force a save of the data overwriting the data held in the database?
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Nov 2, 2011
I have two functios to catch enter key:
Protected Overrides Function ProcessCmdKey(ByRef msg As System.Windows.Forms.Message, _
ByVal keyData As System.Windows.Forms.Keys) As Boolean
Dim handled As Boolean
If keyData.Equals(Keys.Enter) Then
handled = TypeOf Me.ActiveControl Is ComboBox
Me.SelectNextControl(Me.ActiveControl, True, True, True, True)
[Code]...
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Nov 28, 2009
Any example to catch errors and log them to the Eventlog? I would like to catch any error and pass them to my WriteToEventLog function. If I use On Error , how could I catch the Error and pass it to my WriteToEventLog function? I would like to catch the actual error
Public Function WriteToEventLog(ByVal entry As String,
Optional ByVal appName As String = "CompanyName",
Optional ByVal eventType As EventLogEntryType = EventLogEntryType.Information,
Optional ByVal logName As String = "ProductName") As Boolean
[Code] .....
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Jan 5, 2011
I've a control that throws an exception in one of its events and I need to catch this exception. How can I do this?
Example:
Private Sub AxNtlxImage_Reason(ByVal sender As Object, ByVal e As AxNTLXIMAGELib._DNtlxImageEvents_ReasonEvent) Handles AxNtlxImage.Reason
' TODO: Deal with this reason message
Throw New ArgumentException(e.sText)
End Sub
I want to catch this exception from another procedure when it happens.
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Jul 16, 2010
I'm trying to create a user control that will provide a draggable splitter between two panels — exactly like SplitContainer — in a custom IDesignerHost implementation. SplitContainer itself, as far as I can tell, is not an option; it will raise an exception unless used in Visual Studio's Designer.
My implementation would look roughly like this, except that I'm not receiving the necessary mouse events. I've tried event handlers, On* overrides and overriding WndProc in the user control itself, the host control, and the parent form, but I don't appear to receive WM_MOUSEMOVE, WM_LBUTTONDOWN or WM_LBUTTONUP events anywhere. Per this bug report, I should be receiving WM_MOUSEMOVE in "the control designer"; I'm not sure what that refers to in this case.
how I can implement a draggable splitter?
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Jul 22, 2009
I'm trying to create a user control that will provide a draggable splitter between two panels — exactly like SplitContainer — in a custom IDesignerHost implementation. SplitContainer itself, as far as I can tell, is not an option; it will raise an exception unless used in Visual Studio's Designer. My implementation would look roughly like this, except that I'm not receiving the necessary mouse events. I've tried event handlers, On* overrides and overriding WndProc in the user control itself, the host control, and the parent form, but I don't appear to receive WM_MOUSEMOVE, WM_LBUTTONDOWN or WM_LBUTTONUP events anywhere. Per this bug report, I should be receiving WM_MOUSEMOVE in "the control designer";
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May 16, 2012
I received some good advice previously on parallel.foreach vs Task.Factory.StartNew. I have implemented both and have been surprised with the efficiency of both. I used the following link o try and understand exceptions and incorporate it to be notified if a task stops for any reason the program will detect it. Is there any definitive way to do this without wait() or waitall which will tie off the interface and other tasks running at the same time.
Try
pcounter += 1
Dim factory As Task = Task.Factory.StartNew(AddressOf FileParser.Module1.Main)
[code].....
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