using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("---Index Initializer 1---");

        SortedList<int, string> planets3 = new SortedList<int, string>()

        {

            [1] = "Mercury",

            [2] = "Venus",

            [3] = "Earth"

        };

        foreach (var item in planets3)

        {

            Console.WriteLine($"{item.Key}, {item.Value}");

        }

        Console.WriteLine("---Index Initializer 2---");

        var planets2 = new SortedList<int, Planet> {

            [101] = new Planet() { Id = 1, Name = "Mercury" },

            [102] = new Planet() { Id = 2, Name = "Venus" },

            [103] = new Planet() { Id = 3, Name = "Earth" }

        };

        foreach (var item in planets2)

        {

            Console.WriteLine($"{item.Key}, {item.Value.Id} and {item.Value.Name}");

        }

    }

}

​

public class Planet

{

    public int Id { get; set; }

    public string Name { get; set; }

}