get user information

I used to program in Visual Studios .net and on a windows platform you can get user info.
Is that possible to do on an iPad. I want to make a scoreboard and would like to get a user name or even get the users apple id.
Any suggestions?

Take a look at this.

To go further i am not storing just locally but to sql on a server. Is it possible to get user info or the apple id off an iPad?