Question

I’ve a WCF with following 3 tiers:

1. Service
2. BLL
3. DLL.

Could anyone please help me out on:

Which one of the above tier is the best place to catch and log the exception on following scenario:

Scenario 1:

Exception happens on DLL.

Scenario: 2:

Exception happens on BLL.

Also, should I always always wrap the call to BLL from Service on Try and Catch?

Answer 1

it depends on your system here, but I would log the exceptions probably inside the BLL. And mind you “log” not catch! That is – at the end of the catch will stand a rethrow!

I don’t catch anything in the service at all – this is just to communicate with the client – no need to put any logic inside it IMHO.

And of course: catch your expected exceptions where they are thrown and just let the unexcepted pass.

For example:
Scenario 1 – maybe catch SqlExceptions, try handle them and if not wrap them in some DAL-Exception and throw these.
Scenario 2 – maybe catch the DAL-Exceptions from Layer 3 and see if you can handle those or wrap them yet again, …

IMHO it’s almost never a good idea to handle, log and mute all kinds of unexcpected exceptions (catch (Exception)) – the app state will just be very undefined after this.