Active directory authenication

Question

I have a new C#.net 2008 console/windows form application that I need to add security for. I would like to tie all logins together at one time using the active directory. I would like to have windows authenicatiuon setup to use to connect to the sql server 2008 r2 database, I would like to know what role each person has, I also would like to setup a methods to determine what application a user has access to and what their roles are in each application. (For example; a person can have access to app1 and be a manager in the next applicationn theperson would only have a 'general' user role.) Thus i am wondering if you can tell me the following;

1. I would like to know how each person can connect to the database,
2. I would like to see C#.net 2008 code that would accomplish the tasks i listed above or at least accomplish part of the tasks listed above.