using System;

    // see: https://stackoverflow.com/q/47467942/1016343

    public class Program

    {

        public void Main()

        {

            var obj1 = new Test();

            obj1.Count.Dump();

            obj1[7].Dump();

            Console.WriteLine();

​

            var obj2 = new Test2();

            obj2.Count.Dump();

            obj2[7].Dump();

        }

        class Test

        {

            public int Count => 1;

            public string this[int position] => $"2 x {position} = {(2*position)}";

        }

​

        class Test2

        {

            public int Count { get { return 1; } }

            public string this[int position] { 

                get { return String.Format("2 x {0} = {1}", 

                                           position, (2*position).ToString()); }}

        }

    }