.net - Why Isn't The Try/catch Catching The Access Violation
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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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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Mar 1, 2012
I'm trying to call a Dll function which looks like this (in the C/C++ Dll):declspec(dllexport) void execute(char** ReturnMsg, char* serverAddress, char* commandLine)
The VB 'wrapper' function looks like:
<DllImport("TPClient.dll", EntryPoint:="execute", CallingConvention:=CallingConvention.Cdecl, CharSet:=CharSet.Auto, ExactSpelling:=True)> _
Public Shared Sub tg_execute(<Out()> <MarshalAs(UnmanagedType.LPStr)> ByRef returnString As System.Text.StringBuilder, _
[Code]...
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Apr 8, 2009
Im having a access violation error on my QueryPerformanceCounter Statement and im not sure why. I've search the internet for answers but found none.Declaration:
Private Declare Function QueryPerformanceFrequency Lib "kernel32" Alias "QueryPerformanceFrequency" (ByVal lpFrequency As Int64) As Boolean
Private Declare Function QueryPerformanceCounter Lib "kernel32" Alias
[code].....
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Apr 23, 2010
I am using VS2010 release edition with Windows XP, Vista, 7
my programme works fine in XP but fails in Vista and 7.
All I am trying to do is open a OpenFileDialog to get a filename. [code]...
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Jul 5, 2010
I'm been upgrading an application form VB6 to VB2008
I've started getting "Access Violation Exception was unhanded - Attempted to read or write protected memory" error message.
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Apr 26, 2012
I have exactly same problem as guy at [URL] . Quote: I'm using multithread in my application. in each thread, launch a form which has a webbrowser. each browser is controlled by another thread to test some sites. however, sometimes, it has some access violation exception. these exceptions are not beause of cross thread issue since all processing for the browser are using delegate. And the problem is: I can not catch the access violation exception.
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Sep 8, 2010
win7 64bit, VB express 2010.
I'm working on a project. The main form is a MDI parent, it host a control form. on control form, there is a button. when click it, it will start, say 10, threads.
each thread will open a standard alone form (not mdi). on each form, it has a web browser control. when the form opened, it will start a new thread which makes the web browser control load a url, then depends on the links in that url, it will load another url, and loop for some times. then, the thread stops, and the form closes.
for some reasons, I got this weird exception:
AccessViolationException was unhandled by user code. Attempted to read or write protected memory. This is often an indication that other memory is corrupted.
1) the exception happens randomly, and not always happen. when it happens, it is always some code related with the web browser, i.e.
Not (MDIWebBrowser.ReadyState = WebBrowserReadyState.Complete)
or
MDIWebBrowser.Document.Body.InnerText()
2) I put a try catch in, but, it can not catch this exception. If I just close the exception dialog, sometimes, it keeps running without problems. sometimes, it just pauses the webbrowser control.
so, I did some research. it seems many people had the exact same problem. and it seems the best choice is:
[URL]
I checked all solutions suggested, even manually change the DEP, by using "bcdedit.exe /set {current} nx AlwaysOff"
but, the exception still pops up.
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Oct 1, 2011
I have a single user app that I wrote and have been using for more than a year that uses an Access 2003 database. Today, out of the blue, I started getting a DB concurrency violation whenever I tried to update one particular table in the database. After trying to troubleshoot what the problem might be, I just deleted that table and recreated it and the problem went away.
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Jul 6, 2011
I'm creating a database using Access 2007 and Visual Basic 2008.
I'm using the try and catch exception handler in my project. this try and catch are inserted in the Save Record button. here is the code snippet of my try & catch:
CODE:
My problem is that, whenever i add a new record and clicked the Save Record button, the msgbox "Data Update Failed" popped out. But when i recheck, the newly added record was actually successfully saved in the database.
Is there something wrong with my code? The new record is inserted in the database but why does the "Data Update Failed" msgbox was popped out instead of the "Data Saved" msgbox?? I've tried many times but i still cant figure this out. please help.
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Mar 25, 2011
I have a program in VB.Net that receives mails from Outlook, extracts attachments and inserts the attachments into a table through a query. I would like to put the query/queries in a Try/Catch block, but cannot do so as Outlook exceptions cannot be caught, and it gives me an error, and unless I put a very specific exception, I cannot catch it. Is there a workaround?
Edit:
Try
Catch ex As Exception
End Try
Exception is underlined and when I hover on it, it says: "Catch cannot catch type 'Microsoft.Office.Interop.Outlook.Exception' because it is not in 'System.Exception' or a class that inherits from 'System.Exception'". This is affecting all my other code which I'd like to put into a Try/Catch block.
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Jun 19, 2012
The following code causes a "Warning" that Variable is used before value assigned.How do I restructure this Try/catch to eliminate error on the myreader.close command in the Catch part? Code appears to work fine but I dont like Warnings. [code]
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Apr 1, 2011
i have problem when i click a ADD button, there is one null value in the textbox .. so the try catch statemnt is to catch that null value error but after that the catch is success but the button click never stop excute the statemnt till the end of the button event.
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Mar 4, 2009
I have this scenario: in a Sub I have a Try...Catch statement.Within that Try..Catch I call another sub.In that 2nd sub is also a Try...Catch.(see below for example).Now if an exception occurs in the 2nd sub's Try...Catch, which Catch gets excecuted? The 2nd one, the 1st one or both?
Private Sub sub1()
Try
..do stuff[code].....
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Jun 2, 2009
If I throw an exception from within a catch, does the finally (from the catch) still execute? i.e.
Try
..some code with an exception in it...
catch ex as Exception
throw new SpecialException("blah blah" & ex.Message, ex)
[code]....
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Jan 23, 2012
I need to catch log4net exceptions (its own exceptions not app exceptions logged by it). I wish there's a way of doing it this way: [code] I have this code implemented and there's no errors in compilation but i force log4net to have an error (pointing to a non existing database in the config file) and nothing is threw.I've tried the listener aproach: [code] and it's writing the errors to log4net.txt, the forced ones i mean.This last aproach has a couple of drawbacks: it won't append every error to the file, if the error is the same it doesn't write it, i can't get the listener to write every error to that file, only one (I don't know how to fully configure the trace listener, it might be that). Thus it won't append the date and hour to every line wich is a necesity for me. Finally i can't give structure to it (xml). Even if the listener work i need to use the try/catch aproach, since i'm using ExceptionHandling from Enterprise library to log the errors in my app.
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Feb 12, 2010
I am using VB.NET 2005 to create a Windows forms application. I have a procedure named SendMail that creates an instance of Outlook.Application, to send an email from my application. I found the code on this forum, I think.The procedure works fine, but I can't use error handling with it.I call the procedure from a button click event. I put the procedure call in a try/catch block, and the application won't build, with the following error.
Error 68 'Catch' cannot catch type 'Microsoft.Office.Interop.Outlook.Exception' because it is not 'System.Exception' or a class that inherits from 'System.Exception'. C:datadevdmtiQTSQTSv7_1_20100212wQTSQTSReportsCriteria
pt_frmReportViewer.vb 43 21 QTS
Here is the code:
Sub SendMail(ByVal sFile As String)
' Create an Outlook application.
Dim oApp As Outlook._Application
[code]....
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May 20, 2010
i am trying to write a code in which i need to perform a update but on primary keys how do i achieve it
i have written the following code: kindly look at it let me know where m wrong
[Code]...
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Apr 6, 2010
i am trying to write a code in which i need to perform a update but on primary keys how do i achieve iti have written the following code:
Protected Sub rgKMSLoc_UpdateCommand(ByVal source As Object, ByVal e As Telerik.Web.UI.GridCommandEventArgs) Handles rgKMSLoc.UpdateCommand
Try
KAYAReqConn.Open()
[code]....
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Jan 28, 2011
My users are getting this error when trying to update the database:
"Concurrency violation: UpdateCommand affected 0 of the expected 1 records"
All the users are doing is clicking a button which updates a record.No two users are updating the same record or even within the same column. They could be updating within the same row but still not the same record.It seems to be happening when the program is open for a little while and they come back and try to update the database through the program. I have read a little bit about this error but none seem to lead to a clear solution.It seems like the database connection is timing out due to inactivity?Here is my update command:
vb.net
Private Sub btnComplete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnComplete.Click
Me.txtComplete.Text = Date.Today[code].....
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Mar 24, 2012
I have a procedure that is building a PrimaryKey based on values input from a CSV File. There are 4 fields that make up this PK. My code is below.
[code]...
For some reason when it takes the "IF" branch, it gives me the "Violation of PrimaryKey" Error. When I debug the 4 key values, the record does exist in the DB Table. Not sure why it's taking this path. I think I'm not testing the "row" object correctly.
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Dec 15, 2011
I'm having an issue with a concurrency violation when I save my data(only on one form). All other data forms are working fine. This form has a lot of code, so to isolate the problem I added a new form to the project and dragged the table from my datasource, in detail, to the form. this is the only code in the form,
[Code]....
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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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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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Aug 10, 2010
I'm getting 'Catch' cannot catch type 'Object' because it is not 'System.Exception' or a class that inherits from 'System.Exception'. and 'Expression detected' Code underlined in blue: Catch obj1 As Object When (?)
Private Sub OpenJAMem()
Dim num3 As Integer
Try
[code]....
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Apr 16, 2012
I have a project converted from Visual Studio 2005 to Visual Studio 2010. It compiles and runs.
When I prune "unused references's from this project as listed by Visual Studio, the project fails to compile with the subject error message.
In particular one of the "unused refererences" is to "Microsoft.VisualBasic.dll". The IDE does not allow me to add back this particular reference.
What do I need to add back as a referenceto get this items?
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Apr 20, 2010
A few weeks back in reply to a thread, I said then that it's sometimes worse to use a Try/Catch when there's nothing in the Catch!There are exceptions to that I'm sure, but too often the Try/Catch is used with a blank Catch that makes even the developer scratch their heads when the program crashes because they have nothing to go on (by their own doing).DevExpress (and I'm a big fan of their stuff) has a little three minute video that encapsulates that concept well and I thought that you all might enjoy watching it:[URL]
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Jun 12, 2009
I am trying to make a simple demo of a DataGridView bound to a database table. I want to add a row, delete a row, and save the table. I used the IDE to do just about everything. It created the BindingSource when I set the datasource of the DataGridView to a table of a DataSource I added to the project.
Now the only code looks like this:
Public Class Form1
Private Sub DataGridView1_CellContentClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellContentClick
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
[Code] .....
I set the AutoIncrementStep to 1 in my Key field in the dataset (the .xsd). I left the Key field visible in the DataGridView and it seems to be adding the correct Key when a row is added. However, I still occasionally get the "concurrency violation" error if I just mess around with these 3 buttons. Any idea why/how to prevent that?
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Aug 6, 2009
I have a problem running a simple query: "select distinct payee from table". This query is set up in the dataset and is called GetAllPayee.My code goes something like:
Dim dtSources as new Datatable
dtSources =
Me.TblExpenseRecordsTableAdapter.GetAllPayee
Upon running I get the error:Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.The problem is, I haven't set ANY constraints on either the new datatable, or the dataset table (tblExpenseRecords). i.e. there is no primary key etc.
Can someone please help me out with this problem?I have no problems running the query through the wizard where I can view the results successfully.
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Mar 17, 2009
get around the following problem please?I have an Access database which can be accessed by more than one instance of my application (which is) a Form with a DataGridView on it.I populate the DGV with
Form1.Validate()Form1.CHECKLISTBindingSource.EndEdit()Form1.CHECKLISTTableAdapter.Update(Form1.chkDataSet.CHECKLIST) The Access Database can then be updated via the DGV by a button click (which runs the code above (to copy across the latest copy of the DB) and then runs the code below to copy your changes to the DB)
Form1.CHECKLISTTableAdapter.Fill(Form1.chkDataSet.CHECKLIST)
Form1.DataGridView4.DataSource = Form1.CHECKLISTBindingSource
Form1.DataGridView4.Refresh()
The Access table is basicaly a 'Time' Column and a 'Name' Column.
[Code]...
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