using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {   

        var l = new List<int>(0);

        var lc = l.Count;

        var d = new Dictionary<string, int>(4);

        foreach(var k in l) {   

            Console.WriteLine($"{k}");

        }

        d.Add("1st", 1);

        d.Add("2nd", 2);

        d.Add("3rd", 3);

        d.Add("4th", 4);

​

        var rnd = new Random();

        foreach(var kvp in d) { 

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

        }

        Console.WriteLine($"-----------");

        foreach(var key in d.Keys) {

            d[key] = rnd.Next();

        }

​

        foreach(var kvp in d) { 

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

        }

    }

}