We're reviewing one of the company's system's exception handling and found a couple of interesting things.
Most of the code blocks (if not all of them) are inside a try/catch block, and inside the catch block a new BaseApplicationException is being thrown - which seems to be coming from the Enterprise Libraries. I'm in a bit of a trouble here as I don't see the benefits off doing this. (throwing another exception anytime one occurs) One of the developers who's been using the system for a while said it's because that class's in charge of publishing the exception (sending emails and stuff like that) but he wasn't too sure about it. After spending some time going through the code I'm quite confident to say, that's all it does is collecting information about the environment and than publishing it.
My question is: - Is it reasonable to wrap all the code inside try { } catch { } blocks and than throw a new exception? And if it is, why? What's the benefit?
My personal opinion is that it would be much easier to use an HttpModule, sign up for the Error event of the Application event, and do what's necessary inside the module. If we'd go down this road, would we miss something? Any drawbacks?
Your opinion's much appreciated.
Never1 catch (Exception ex). Period2. There is no way you can handle all the different kinds of errors that you may catch.
Never3 catch an Exception-derived type if you can't handle it or provide additional information (to be used by subsequent exception handlers). Displaying an error message is not the same as handling the error.
A couple of reasons for this, from the top of my head:
If you know how to handle a specific exception (and reset the application to pre-error state), catch it. (That's why it's called exception handling.)
To handle exceptions that are not caught, listen for the appropriate events. When doing WinForms, you'll need to listen for System.AppDomain.CurrentDomain.UnhandledException, and - if your doing Threading - System.Windows.Forms.Application.ThreadException. For web apps, there are similar mechanisms (System.Web.HttpApplication.Error).
As for wrapping framework exceptions in your application (non-)specific exceptions (i.e. throw new MyBaseException(ex);): Utterly pointless, and a bad smell.4
Edit
1 Never is a very harsh word, especially when it comes to engineering, as @Chris pointed out in the comments. I'll admit to being high on principles when I first wrote this answer.
2,3 See 1.
4 If you don't bring anything new to the table, I still stand by this. If you have caught Exception ex as part of a method that you know could fail in any number of ways, I believe that the current method should reflect that in it's signature. And as you know, exceptions is not part of the method signature.