How to check roles for selected user?

I was following a tutorial on the asp.net site about Assinging Roles to User. On the "Checking the Roles the Selected User Belongs To" step, it has this code: 
1 private void CheckRolesForSelectedUser()
2 {
3 // Determine what roles the selected user belongs to
4 string selectedUserName = UserList.SelectedValue;
5 string[] selectedUsersRoles = Roles.GetRolesForUser(selectedUserName);
6 // Loop through the Repeater's Items and check or uncheck the checkbox as needed
7 foreach (RepeaterItem ri in UsersRoleList ...