I have a vb.net desktop application and I am using thread.Abort() there.
I am getting system.threading.threadabortexception error.
Below is the error messagebox i am getting but not everytime.
Unhandled exception has occured in your application. If you click
Continue.....
Thread was being aborted.
Please suggest how to avoid this errormessage.
Please suggest how to avoid this error message.
The best, and correct, way to avoid this is to not call Thread.Abort(). Thread.Abort() is really a bad idea in general. Instead, you should build your routines around the cooperative cancellation model built in the framework.
Related
I am studying OOP, and I did not understood the concept of exception.
What are the correct uses of exceptions?
Why use exceptions when you already know a possible exception?
For example, I have seen a code sample where the programmer needed to access a file, and had an exception in case the file does not exist. Something like "catch(fileDoesNotExist e)".
Why not use an if to verify before take the action? And use exception only for not known issues, for logging or error messages.
The idea behind the concept of exception was to decouple the error handling code from the "normal" behaviour flow control. That lets to manage/handle the exception further up the call stack.
Historically, with structured language, error handling code (file opening error,...) was mixed within the "business" application code. It was also painful to improve the code in order to manage new error codes.
What are the correct uses of exceptions?
If it is not normal that your file doesn't exist or cannot be opened => it is considered as an exceptional situation => exception => exception handler
Why use exceptions when you already know a possible exception?
To decouple the business application code from the error handling. That eases source code readibility and maintenance.
Exception:
Exception is that interrupt(break) the normal flow of the program.It's thrown at runtime.
Exception Handling
Exception Handling is a mechanism to handle runtime errors such as ClassNotFound, IO, SQL, Remote etc
In java there are mainly two types of exception that checked and unchecked.Other than Error is there
Hierarchy of Exception classes in Java
Why use exceptions when you already know a possible exception?
basically exception handling use to mainly,we assuming in that our particular code will occur some(NullPointerException,ArrayIndexOutOfBoundsException etc..)exception.If we not Handle that,program will break.Actually that Exception it may or may not will happen.But so we need to handle normal flow of the program it occurred or not.Otherwise after that particular code section not executing.
We are using the MSXML2.ServerXMLHTTP60Class to make HTTP requests. Usually this works fine, but on some occasions when the url cannot be resolved, the send method fails. In this case an exception is thrown.
The problem is that we program in Microsoft Dynamcs NAV C/AL code. This language does not support error trapping (try catch).
Does anybody know if there is some setting in the ServerXMLHTTP60Class that prevents the send method from failing?
Note: the send method fails, so checking the response status is not an option.
Thank you!
Depend your on version of Nav you have different ways to handle exeptions.
In Nav 2016 there will be try function
In previous versions you should use if codeunit.run then syntax to catch the exception and getlasterrortext to get error message.
For more information read Vjeco
Another option to avoid unhandled exceptions is to write a wrapper class around ServerXMLHTTP60Class that will catch all exceptions and handle them in the way you like.
Is it possible to have some sort of global action/event that triggers in the event of a fatal error? I'd like to be able to have my program write an error file and/or perform other "last breath" (no idea what else to call it...) action if a fatal or unhandled exception occurs that would cause the program to close or crash. Is such a thing possible?
I'm programming in VB.NET v4 using VS2010, if that is important. Also, all users of my app will be authenticated as an administrator (if that matters?).
It depends on what kind of application you're writing, but these may help:
Application.ApplicationExit
Application.ThreadException
AppDomain.UnhandledException
Yes there is AppDomain.UnhandledException Event. And no you do not need any permissions to use it.
I have created a vb.net program and released it to the customer. They are running the exe and at times the program crashes unexpectedly and display the message: "... has encountered a problem and needs to close"
I know I should have added code to handle the exception, but is there a way that I can find out which line in the program caused the error? What is generally as good way to track errors in a program after it has been released?
Thanks
for this kind of i-don't-know-where-to-look issue, i trapped exception at application level with the Application.DispatcherUnhandledException event :
http://msdn.microsoft.com/en-us/library/system.windows.application.dispatcherunhandledexception.aspx
and then in the event handler i get the StackTrace and display it in a MessageBox / dump it in a file, along with the exception.Message.
Next i offer the user the choice to re-launch the application.
've been running through the MSDN help documents to get a hang of Visual Basic. After trying out the example using timers --one drags a label and timer component into the designer and adds the following to the components subroutine
Label1.Text = My.Computer.Clock.LocalTime.ToLongTimeString
The output for the immediate window during debug is the following
A first chance exception of type
'System.InvalidCastException' occured
in Microsoft.VisualBasic.dll
A first
chance exception of type
'System.InvalidCastException' occured
in Microsoft.VisualBasic.dll
The same error occurs on a previous MSDN example using a context menu component. Should I Try...Catch...Finally this error and try to move on? Or, am I dealing with something much more serious?
When you see something about a first chance exception, it only means that an exception was caught within the code you called but does not necessarily mean that the code failed. If the code runs without causing your program to crash and returns a valid value, then do not have a problem. You will also see output in the debug window about first chance exceptions when you implement your own try/catch blocks.
In the Debug menu -> Exceptions, you can enable the debugger to stop when an Exception is first thrown, even if it would be caught later; if you want to find out what's happening, this is the easiest way to do it
In the first chance exception examine the details of the exception. You should see a stack frame/trace property. In there you should see what line the error occurs on. This should help you.
In the IDE try going to Tools > Options > Projects and Solutions > VB Defaults and setting Option Strict to 'On' - this may help catch casting problems when you compile your project rather than when you run it.
A 'first chance execption' does not necessarily mean you have a problem in your code. It could mean the IDE or the compiler or any other involved component encountered and handled an error and in the process the debugger is notified and the exception is being reported to the immediate window. This is an excellent post on the topic:
http://blogs.msdn.com/davidklinems/archive/2005/07/12/438061.aspx
A quick and easy solution for debug and diag of First Chance Exception is :
AppDomain.CurrentDomain.FirstChanceException += CurrentDomainOnFirstChanceException;
and then
private void CurrentDomainOnFirstChanceException(object sender, FirstChanceExceptionEventArgs firstChanceExceptionEventArgs)
{
if (firstChanceExceptionEventArgs.Exception is NullReferenceException)
{
// do your handling and debugging :)
}
}
Multiple First Chance Exception during the runtime can cripple the performance of your application because exception handling is expensive. Especially in web apps. You can add this handler and look at specific first chance exceptions and try to avoid/correct them.