C#的索引器

public class Person
        {
            private string _name = "No one";
            public Person(string name)
            {
                _name = name;
            }
            public string Name
            {
                get { return _name; }
            }
            public string this[string key]
            {
                get
                {
                    if (key == "Name")
                        return _name;
                    return null;
                }
                set
                {
                    if (key == "Name")
                        _name = value;
                    return;
                }
            }

            public string this[int key]
            {
                get
                {
                    if (key == 0)
                        return _name;
                    return null;
                }
                set
                {
                    if (key ==0)
                        _name = value;
                    return;
                }
            }
        };public class Person
        {