UserID from User Table

Hello, all I am trying to make a simple request to retrieve the UserID from the Users Table after they have registered the user. 

I have read that there are calls on Commerce Server to get this info:

PrincipalInfo.CurrentPrincipal.GetContactId()

For user name and email:

var customerContact = PrincipalInfo.CurrentPrincipal.GetCustomerContact(); 

However I cannot find anything on the CMS side that will do the same thing. Any help would be appreciated.