public class User
{
    public string Name { get; set; }
    public string Surname { get; set; }
    public int Age { get; set; }
    public string Country { get; set; }

    // This comparer will be used to find records that exist or don't exist.
    public class KeyFieldComparer : IEqualityComparer<Person>
    {
        public bool Equals(User u1, User u2)
        {
            return u1.Name == u2.Name && u1.Surname == u2.Surname;
        }

        public int GetHashCode(User u)
        {
            return u.Name.GetHashCode() ^ u.Surname.GetHashCode();
        }
    }
}

List<User> csvList;
List<User> oracleList;

// This will filter users that are in the CSV file that don't already exist in oracle.
var newUsers = csvList.Except(oracleList, new User.KeyFieldComparer());

foreach (var newUser in newUsers)
    InsertNewUser(newUser);