using System;

using System.Collections.Generic;

​

public static class Program

{

    public static void Main(string[] args)

    {

        var item = new ItemWithIndexer

        {

            ["1"] = "value"

        };

​

        Console.WriteLine(item["1"]);

    }

}

​

public class ItemWithIndexer

{

    private readonly Dictionary<string, string> _dictionary = new Dictionary<string, string>();

​

    public string this[string index]

    {

        get { return _dictionary[index]; }

        set { _dictionary[index] = value; }

    }

}