Take a look at AFContact.GetCurrentUser(). The AFContact object for the current user is returned. If a contact for the current user does not exist, then null reference (Nothing in Visual Basic) will be returned.
Or AFContact.FindContact( PISystem , Name);
The Name or the full CanonicalName of the contact to find. When the full CanonicalName is specified, the AFActiveDirectoryProperties.UserFolder setting is ignored.
Return Value: The AFContact in the PISystem which matches the name.