How To Catch Unhandled Exceptions In Custom Controls
Jan 5, 2012
Is there anything similar to the MyApplication_UnhandledException for an user control in VB?
I would like to have a central point where to catch all unhandled exceptions of a user control, without propagating the exception to the application that uses the user control. I made some test raising an exception in a method of my user control where there is no try/catch code (of course in the true project all methods have a try/catch block). The exception was caught by MyApplication_UnhandledException event of the application using the user control. But this is too "far" from the point where the exception happens and in worst case the user should restart the application.
I would like to realize a behaviour for the user control in order that if the user control fails, the exception is not propagated till the application, but just caught at user control level.
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Oct 19, 2011
I would like to catch any exceptions from any method in a class so that I may record class specific data to the exception for logging before it is passed up the stack. I know that I can put a try-catch in every method of the class, but there are many methods and It seems there should be a more efficient way. Example of what I am currently doing:
public class ClassA
{
private int x;
[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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Jun 10, 2009
When you use Try Catch for Exceptions, will
Catch ex As Exception
Catch any possible error that could occur or do you have to catch each exception separately?
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Feb 4, 2011
Is there a way to catch these Exceptions? (I am not looking for "just put try/catch or on error goto around them"). I am trying to find out if these errors can be caught by something outside of them.[code]...
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Aug 17, 2010
Is there a way to catch all SQL exceptions in a project? I have several gridviews and multiple sqldatasources and most of the errors are going to occur when a user enters something incorrectly or in the wrong column. So how do I stop the Server Error in /Project page from showing up?
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Mar 25, 2011
I am working on an app that uses a third-party charting component.It is a .Net component. There have been some occasions when exceptions have occurred inside the third-party component code, but my try/catch is not trapping them.Should they get trapped?My code is structured roughly like this:[code]I have since found and fixed what was causing the exceptions, but I would have thought that this should trap them. What happens when I run in the IDE is that it crashes and Visual Studio throws up a page telling me there is no code available to debug, and no disassembly available.Fair enough, but I repeat - why doesn't the exception get trapped?
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Oct 13, 2010
Is there some special way to catch exceptions in finally block ?
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Apr 8, 2011
I have a SqlDataReader and I want to trap any exceptions with Try Catch Finally if the reader =cmd.ExecuteReader() statement fails. If this statement throws an exception do I need to close the reader? If so, where. Wherever I place the reader.close() statement I get an error that the reader has not been assigned a value yet.
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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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Apr 6, 2011
[Code]...
Notice the catch (Type) instead of catch (Type myVariable). Is this possible with VB.NET, or do you always have to declare a variable when you catch exception types, like so:
[Code]...
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Jan 25, 2010
so i have a Method that is going to made Thread Safe. can i have something like this in the Method:
Public Class Q Private Shared ASD As New MyException("") Public Sub W Throw ASD if multiple threads attempt to throw the Shared exception ASD, will there be an error in the catching part? The alternative of course is to: Throw New ASD but i'm just checking to see if the first way is thread safe
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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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Jan 22, 2009
An application raises the UnhandledException event when it encounters an unhandled exception.
For instance, you can use this event to ask user send you a report by email.
[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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Feb 28, 2012
I read that if I put this code in ApplicationEvents.vb
[code]...
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Apr 2, 2011
I have an assembly containing a number of classes. This is a class library type assembly, not a windows forms application. It's also single threaded.Is there a way to catch all un-handled exceptions so that I can log them?
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Jan 31, 2012
I wonder how to use statement handles exceptions?Do I need to wrap the using statements with a Try/Cath/Finally clause in order to be sure that the SqlConnection object is closed and disposed even if the containing code throws an exception? [code]
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Jun 12, 2011
In my code I am trying to come up with the following messages using a try/catch Unhandled exception has occurred in your application. If you click continue, the application will ignore this error adn attemp to continue. If you click Quit, the application will close immediately.conversion from string """" to type 'integer' is not valid Warning Icon followed by 3 buttons one that saids the DETAILS, another for CONTINUE, and one for QUIT.Here is part of my code. I did use Try/catch correctly, but it doesnt say the message the way i described it above ..
[code]...
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Apr 25, 2011
This is part of my block which handles incoming messages via TCP. Sometimes it sends scrambled messages which are unpredictable and i need a Try + Catch block for it:'
[Code]...
I can either get "Input string not in correct format" or "typecast not valid". But this is simply supposed to be routine to run into and be able to handle. but that stupid error message keeps popping up I've heard of JITDebugging, should I use that?
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Sep 24, 2011
I am catching sql exception from databse as shown below.[code]Now I want to throw exception by adding some userfiendly information,Like below.Throw SQLexception + "my message.....".
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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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Jan 16, 2010
Is the only way to create custom exceptions to inherit from System.Exception?
I wish to create a class that can be thrown as an exception but i do not wish to inherit from System.Exception because i have a base [Object] class in my library which all my classes should inherit from and i wish my custom exception class could also inherit from it.
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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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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 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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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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Oct 5, 2009
how to use them then before, but am still a little confused with a few aspects. Here goes:
1.) Lets say you have a method that checks for a certain condition(s) and if it fails Throws an exception. Does it have to be in a try/catch block? Meaning can the "Throw" statement exist in a block with no try/catch statement?
2.) Now lets say we have a method that has a try catch block and in it there is a throw statement. When the throw statement is executed does it first try to find an appropriate catch block in the same method or does it immediately go back to the calling method without looking at the catch statements in the current method where the exception was thrown?
3.) I created a custom exception class that inherits from ApplicationException. Next I created a method which has a catch block that catches this type of exception and does some action. Is the System(i.e CLR) smart enough to throw an exception of this type, or does it only throw exceptions from SystemException?
4.) I know that some people are more liberal in their use of exceptions and others use it more sparingly when truly strange stuff happen like the DB going down. I am writing code where I am getting some info back from the database, converting it and then storing it. Sometimes there might be data that comes back from the database and other times the field is empty and the Null value comes back. Therefore in the instances where Null comes back from the database I should not convert the value to anything, since I will get an error. What should I do in this situation? Should I let the CLR throw the exception when it goes to convert the Null value or should I check for the Null value and if it exists not convert?
5.) In general when I throw exceptions, is it sensible to only throw exceptions of the type Application Exception or are there instances where the programmer throws exceptions of the type SystemException?
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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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May 13, 2012
This may be a debugger issue, but here goes:I have this piece of code:
Private Function Connect() As Boolean
Try
sessionBegun = False[code].....
My intention is to 'convert' the low level exception into something more meaningful, so I throw an exception of my own creation. I want this to bubble up to a place where I can handle it.However what is happening is my debugger breaks and tells me that an exception of type "QuickBooksConnectionException" was thrown.I know that, I just threw it, why are you catching it? From what I've read, this ought to work, and there doesn't appear to be an analogous Java throws keyword, so perhaps it is my debugger.
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