Exit Application On Error in a C # Library

Question

It is a silly question I admit. So, apologies if this wastes your time but I just cannot find out a solution.

A WinForm Application which has a Class Library. I use Log4Net dll for logging information.

On Button_Click, I call a function in the Class Library which might throw an error. So, I have the contents of the function inside a try-catch-finally block. In the catch, I write log statements (using Log4Net dll).

Now, that an error has occurred, I want a Message to be shown to the UI. And after a Message is shown, I want it to quit.

How do I pass the control from the catch block of the Class Library back to the Form code so that I display a message and then quit?

Hans Olsson · Accepted Answer · 2010-11-11 08:14:50Z

Just call throw without any parameters after you've logged the error in the exception handler in the class library and it'll rethrow the exact same exception with the same callstack etc.

Then let your form catch it and handle it as you want.

Adriaan Stander · Accepted Answer · 2010-11-11 08:16:03Z

In the Class Library Method, in the catch, rethrow the exception, so that it can bubble up to the form.

In the form Button_Click wrap the Class Method call in a try catch, and in the catch display the message and exit.

Mike Clark · Accepted Answer · 2010-11-11 09:20:19Z

0

The library should probably re-throw the exception after logging about it.

class Form { OnClick() { try { library.Routine(); } catch(Exception e) { // messagebox // exit } } } class Library { public void Routine() { try { // stuff } catch(Exception e) { logger.error("error in routine", e); throw; } } }

edited Nov 11, 2010 at 9:20

answered Nov 11, 2010 at 8:17

Mike Clark

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2 Comments

Magic Over a year ago

Thanks! Let us assume that I have it two levels deep. The Form calls a ClassLibrary1, which calls ClassLibrary2. If I were to log the error in ClassLibrary2, then in ClassLibrary1, I can only throw and not do any logging in the Catch Block of ClassLibrary1.

Mike Clark Over a year ago

@Magic. I think that will work, and It's really up to you. Most of my projects have logging at multiple levels. I try to organize it reasonably well in most places, so that most of the time my exceptions are only logged once. In many cases, though, I prefer to risk a little redundant logging over the chance of not getting any logging at all, so I sometimes end up logging an exception twice or sometimes even 3 times. Like I said, I try to avoid it, but it really depends on who is using the libraries and for what.

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