My `Person` class has two properties; name and surname, and a function that returns the first name and the surname together.

Is there anything that can be done better? Anything that is done poorly?

    public class Person
    {
        private string Firstname { get; set; }
        private string Surname { get; set; }

        public Person(string firstname, string surname)
        {
            this.Firstname = firstname;
            this.Surname = surname;

        }
        public string GetFullName()
        {
            string fullname = String.Format("Firstname is: {0}, Surname is {1}", Firstname, Surname);
            return fullname;
        }
    }