>Hi everybody,
>
>The new question, if I may.
>
>1. How can I see the actual code of the system classes?

This only recently became available. It requires VS 2008 to do this automatically, here's a link which goes into detail about how to get it all installed:

http://weblogs.asp.net/scottgu/archive/2008/01/16/net-framework-library-source-code-now-available.aspx

If you don't/can't go that route, download Reflector from www.aisto.com/roeder/dotnet/ - it will let you open any .NET assembly and it will let you view a decompiled version of the source code.

>2. Is the common practice to just trap the exceptions, say, if I want to add a user(s) to the role(s) and some of them are already in that role, I'm currently getting an exception with some helpful message.

Yes, it's standard practice to only trap exceptions which you can handle, which usually isn't just "Exception", but a specific type of exception (or exceptions). Having said that, sometimes you have to capture the generic "Exception" type because no other (more specific exception) type is available.