Handling Exceptions With A Specific Error Code Condition?
Apr 28, 2012
When two computers are connected through TCP, and one of them closes and breaks the connection, it throws error 10054 "Remote host forcibly closed the connection".I want to handle this error because I know it will happen more often than not with the application I'm building. In System.Net.Sockets.SocketException, there is an on the error code. But when I run the program, the exception that is being thrown is System.IO.IOException, and the GetType for IOException is the socket exception. I don't know how to handle the socket exception if it's not the root cause of the exception.
Here is the code for my Try Catch block:
For infiniteCounter = 1 To 2
infiniteCounter = 1
[code].....
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Sep 23, 2010
Part of my assignment is to check if input to Group Number and Number of Units are correct input by making error handling exceptions...
I have to check the following:
a) group number is neither 501 nor 062
b) number of units are NOT numbers
c) number of units is NOT a positive number
So my first question is, am I checking correctly? 2nd question is, How do I make sure my Exceptions will pertain to their correct respective things (a, b, and c.. above)?
[Code]...
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Jun 2, 2009
All of us use the try catch blocks. But what is the best way of handling errors within custom functions?Display a messagebox to the user when the exception is thrown (if possible within the function), or return a value indicating that an error was found within the function?
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Apr 18, 2011
I have set up a process to create new tasks to handle file processing. A problem arised where I received and unhandled exception error and just clicking on the continue button, the main process continued to run. Now I also found that within the child task I was having a file conflict error and as the tasks run as separate .exe i was under the impression that everything would have been thread safe. So for the first issue here is the task creation in the main process..GProcess is a complete project on its own consisting of 6 classes. This is added as a class library reference to the main process class form1
Public Class Form1
..Private parser as GProcess.module = new GProcess.module()
dim factory as new taskfactory
[code].....
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Aug 29, 2011
How does one handle unhandled exceptions in a DLL? VS doesn't give me the option to add Application Events, I'm guessing because it's a DLL. Do I just have to do it in the main app?
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Sep 29, 2010
This was a difficult question to google. I have an Order class with a couple of dozen properties such as ClientReference, ShipMethod, etc. I use databinding to bind this class to an Order form. If a user enters an invalid shipping method, an exception is raised in the ShipMethod property and a validation error is displayed to the user. But I'm trying to use the same Order class within an OrderImport class whose job it is to take a flat file and create multiple orders. The problem occurs if I'm assigning to a dozen of the order fields consecutively, and say the first one causes a validation exception. If I have all dozen assignments occuring within a single try-catch block, the next 11 assignments will be skipped and I'll only be able to record one validation error. I could solve the problem by doing a dozen separate try-catch statements, but that doesn't seem very elegant.
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May 21, 2010
What are some of the most common mistakes you've seen made when handling exceptions?It seems like exception handling can be one of the hardest things to learn how to do "right" in .Net. Especially considering the currently #1 ranked answer to Common programming mistakes for .NET developers to avoid? is related to exception handling.
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May 18, 2010
If any directory within a set being searched by the [URL] or [URL] methods contains a junction point, the entire method fails and returns zero results on my tests under VB 2008. I would like to make the call more robust: to return the folders or files not blocked by access restrictions and to note the folders which were blocked. Do those methods offer a means to do this, or is a recursive folder-by-folder call necessary?
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Oct 21, 2009
So I've made this control that inherits from the treeview control and basically loads objects from active directory into a treeview (url...).All working fine, but as this is the first custom control I have made that I have intended for other people to use, I'm not quite sure how I should approach error handling.I mean, obviously I shouldnt do something like show any exceptions in a messagebox because that might not be what the person that is using the control wants to happen. So do I just write out exception messages to the debug window? Do I swallow exceptions (guessing not)? Do I just totally ignore them so that they are thrown in the user's project?
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Jun 8, 2010
i created a Class library (.dll) and loaded it as reference into a main project. In the code for the class i've handled exceptions using try..catch subs, however when debugging the main project exceptions that are handled in the DLL still get thrown! (the class ".vb" file gets loaded into the debugger and the line of the exception shows up)
Up till now i've found it useful that when an unhandled error occurs in the imported reference, it shows up in the main project with tracing back to the referenced class. But i dont want the exceptions that are handled in the reference class to be thrown when debugging the main project!
As you can see the exception thrown was handled with try...catch this class exception.vb belongs to the project that created the class library (.DLL that i referenced). i didnt even load the project that built the reference so it amazes me that it could find the coding class to begin with.
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Sep 14, 2009
I have a routine that is called when an unhandled exception occures.It is called by the MyApplication_UnhandledException method in applicationEvents (which handles Me.UnhandledException)
I am looking for some code that manages disects the data provided to generate information that is of benefit to the debugging team.
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Sep 28, 2011
I am writing a class library that envelopes an USB device driver. This device has its own class library, provided by the hardware vendor.
Very often, especially if you handle with old DLL or COM assemblies, there are methods (functions to be correct) that return TRUE if all was OK, or FALSE if any error happen. Often these methods return information about the error in one of their parameters or separately in a GetLastError method or even if in an OnError event.
Now, normally I handle all native .NET exceptions in my class libray handling locally or re-throwing to the client if the error is useful to know. But what to do with all other errors that are hidden in the vendor's methods? (in the true I have no exceptions, but only returned TRUE or FALSE values).
Let's make an example with the method "CONNECT" that connect the client to the USB device.
I envelope the method in this way:
Public Sub Connect()
oVendorDevice.connect()
End Sub
now if any connection error happen, the vendor's connect method return FALSE. But I do not know why the connection failed. To know why the connection failed I have to call (for example) the method GetLastError that gives me information about the error. (but do not forget that other vendors use other strategies like returning the error in a method's parameter or in a OnError events.
Now, in order to follow a good .NET exception handling strategy I could write something like this:
Public Sub Connect()
Dim res As Boolean = oVendorDevice.connect()
If res = False Then
[Code].....
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Feb 20, 2011
Code:
Public Function ScreenScrapeHtml(ByVal url As String) As String
Dim objRequest As WebRequest = System.Net.HttpWebRequest.Create(url)
[code]...
If it cant reach a URL it will give me this error:
Code:
Webexception was unhandeled:
Dim sr As New StreamReader(objRequest.GetResponse().GetResponseStream())
How I can add some error-handling to this code? Like if it cant reach a URL.
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Oct 6, 2011
I have a delete button in a datagridview. The button works fine however when there is nothing to delete it throws an index out of range exception. Now I know for a fact people are going to click that button even though there is nothing the I am presuming the best course of action is going to be a try/catch but I am not sure how to do it. My code is as follows,
Private Sub DataGridView1_CellContentClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellContentClick
If e.ColumnIndex <> 7 Then
[code].....
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Jul 8, 2009
I have a VB.NET Application and I am developing a deployment project in VS 2008.
I need to give the user the choice to allow the application to start when windows start (but this should be optional)
Then in my application there should be an option to remove the application from the windows start up folder.
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Apr 26, 2010
I used the following code to click mouse on the specific co-ordinates on an open windows application
Private Declare Sub mouse_event Lib "user32" (ByVal dwFlags As Long, ByVal dx As Long, ByVal dy As Long, ByVal cButtons As Long, ByVal dwExtraInfo As Long)
Private Const MOUSEEVENTF_LEFTDOWN = &H2
[code].....
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Aug 11, 2011
Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) _
Handles Me.Load, Me.FormClosing
MessageBox.Show("form_load")[code]....
While closing the form I observed that the Form1_FormClosing method is fired first, and then Form1_Load second. Why is this order chosen? Why doesn't Form1_Load get fired/entered first, and then Form1_FormClosing second?How does .NET choose which method to fire first, of the two that handle the same event?
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Dec 6, 2009
I'm encountering some rather strange behavior in the VB2008 IDE regarding exceptions. I tried to explain what I need as best I can in the title, but I'm not sure there's a succinct way to describe it.I'm not the best programmer in the world to say the least, so sometimes I do things that generate exceptions when I try to run them (This is why we test things continually, right?). Typically, in addition to the Exception Assistant popping up and giving a suggestion, the IDE highlights the code that caused the Exception in the Code Window.
Well, today I went back to a project I had been working on after putting it on hold for awhile, and while the Exception Assistant still pops up when there's an exception, the IDE doesn't auto-scroll and highlight the offending code anymore. I have no idea why it does this, nor do I know how to fix it. Resetting settings from the Import and Export Settings Wizard didn't fix the problem, and neither did trying to reinstall VB2008. Is there some setting, obvious or otherwise, that would cause this?
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Apr 27, 2010
I have a form where it is validating three fields. I want to have it so if an exception has been thrown in any of the three fields that the code that is in the button does not run and it redoes the validation.
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Jul 9, 2010
I Have just been watching a video on throwing Exceptions. Are you supposed to throw System.Exceptions from within your custom classes. to the calling code, Which other way can they communicate. I have read in several places it is bad practice to throw SystemExeptions.
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Dec 26, 2009
I've just skipped around a few inbuilt VB classes' methods which throws exception. of all that i've came across, methods may throw multiple exceptions but ALL of them are exclusive, meaning there is no way 2 exceptions will ever occur simultaneously, yea and i was trying to make my class throw 2 exceptions simultaneously, hence this question, must all exceptions be exclusive?
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Aug 14, 2011
wrote a program with Regex condition but it shows me Twice the first condition (<H1>Welcome to my Homepage</H1>)what is my problem?i enable multiline property of Textbox1
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim l As New Regex("<(H1|H2)>.*?</(H1|H2)>")
[code].....
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Sep 8, 2009
I have an object, say Order where if an error occurs, it raises the ErrorOccurred event. If I'm running some code in say, the codebehind for a .aspx page with an public Order registered as WithEvents and I want to check to see if an error has occurred before I run more code, how do I do this? I can't simply check theOrder.ErrorOccurred. Do I have to create a local boolean flag that switches over in the event handler (OnErrorOccurred)?
Example:
Public WithEvents theOrder As New Order
Public Sub DoStuff()
theOrder.DoSomething()
If theOrder.ErrorOccurred Then
[code]....
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Jan 20, 2009
I want my program to open a specific tab in condition that "Profiles.txt" is not found. It already opens the Control Panel, but it needs to go to the "Add Players" Tab in the Control Panel automatically.
Is there a way to do that?
Also, I have a couple of advanced tabs that should be disabled or hidden until certain conditions are met.
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Nov 19, 2011
on the msdn pages describing classes etc, there are a lot of properties and methods mentioned from classes. But is there a kind of property of a class or method which gives te collection of expected errors ?i ask this because in the try catch statement you can specify the exceptions and errors you want to catch, but
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Oct 6, 2011
Using VB.Net and Sql Server Query
[Code]...
The above query is showing error as "Incorret syntax near a" What is problem with above query, whethere like condition is used properly or not.
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Feb 16, 2010
I cannot figure this one out.. I have a background worker that will perform a task streaming data from some webpages. this data is then passed back and displayed in a gridview. It has been working fine.
I've recently implemented a listbox, which its values will be passed into the function that the background worker will perform as parameters, originally i had taken a single value from a textbox.
Now, I thought maybe it had something to do with the listbox, so I used a static value, just a simple String, as the parameter, and again, I get the TargetInvocationException was unhandled.. There's no difference in how I perform the task I'm trying to have the backgroundworker complete, the only difference is where it exists in my if condition statement:
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles ScrapeSites.DoWork
Dim results As ArrayList
Dim worker As System.ComponentModel.BackgroundWorker = DirectCast(sender, System.ComponentModel.BackgroundWorker)
[Code]...
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Nov 10, 2010
I never got into detailed error processing too much when I played in VBA/VB6 a lot. Mostly then, if you ran into a user error (such as some input of theirs failing a validation test of some kind), you popped a MsgBox() with some error information and the critical (or warning) icon, and safely aborted out of the code
In .NET, my reading basically points to exceptions as the end-all in error handling. It looks to me that if you know a spot of code where a user can screw up, you're supposed to catch it with either try...catch blocks (for things like data conversions), or standard if...the...else constructs for other things, and then throw a new exception if needed.
Isn't throwing an exception essentially a forced crash of a program in a sense (granted, you get the option of continuing)? Or are exceptions geared specifically for things like data conversion errors and other "things that shouldn't happen", and resume use of MsgBox() and friends for minor user screwups?
Consider the case of where you have a TextBox that is only supposed to accept numeric data (or heck, just a specific set of characters). Barring some other trick that lets you restrict that field (let's just assume it's freeform, programatically), it would seem a bit of a waste to throw new exceptions everytime they type in an invalid character, or even if the error checking doesn't happen until they press a submit button (like on a webpage). Popping a MsgBox() seems more sane in that case.
So what's the straight dope on exceptions and throwing new ones on user errors? How about if your program also exposes a programmatic framework? Bad usage of one of the programmatic functions definitely seems like new exception territory to me.
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Feb 10, 2011
I have a form called LogIn.vb which has no errors. After log-in, it opens the MainForm.vb which IsMDIContainer property is set to true. From the MainMenu, it opens a child form called Assure_Benefits.vb So far no problem up to this point. When Assure_Benefits.vb loads, it displays 2 DataGridViews with datasourses from my 2 tables in my database.
There is still no problem with the loading. Now, to show the difference between different user types, I only allow the admin to edit the DataGrid. SO I set the readonly property to true when UserType = "user".
I have no problem doing that. My problem is I want to add some codes besides the readonly being set to true and false but other codes are not executed and the program does not display any errors at all. i tried to add messageboxes on the if and else conditions to try if added codes will work but even the messagebox does not appear though the codes next to it are properly executed.
When my Assure_Benefits.vb loads I call for the subroutine below.
Private Sub SetControlProperties()
If LogIn.UserType = "admin" Then
MessageBox.Show("Yes") 'This line is not executed
[CODE]...
I can't seem to understand why the first code is not executed when the next codes works fine.
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Mar 6, 2012
When I deployed my project on a server, in certain circumstances, I get an error page that indicates I should create a custom error page. I was wondering how exactly I would implement this custom error page the server asks for to give me a precise and helpful message or preferably, how I would get the error to just display on the main page?This is the error message I got below
Runtime Error
Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.
Details: To enable the details of this specific error message to be viewable on remote machines, please create a <customErrors> tag within a "web.config" configuration file located in the root directory of the current web application. This <customErrors> tag should then have its "mode" attribute set to "Off".
<!-- Web.Config Configuration File -->
<configuration>
<system.web>
[code]....
Notes: The current error page you are seeing can be replaced by a custom error page by modifying the "defaultRedirect" attribute of the application's <customErrors> configuration tag to point to a custom error page URL.
<!-- Web.Config Configuration File -->
<configuration>
<system.web>
[code]....
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