I was doing a code review and came across something odd which I've never seen before. The developer decided to create a sub-namespace just to contain all the assembly's exceptions.
I thought I had read that this was explicitly not a good use of namespaces and that exceptions should be kept at the "lowest" namespace from which they are thrown, but I haven't found anything on MSDN (or anywhere else for that matter). At the same time, it seems odd that I haven't come across this before in the framework itself or the third party libraries I've used.
Are there any guidelines exist that would push away from keeping all exceptions in a .Exceptions sub-namespace?