using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var cities = new Dictionary<string, string>(){

            {"UK", "London, Manchester, Birmingham"},

            {"USA", "Chicago, New York, Washington"},

            {"India", "Mumbai, New Delhi, Pune"}

        };

​

        cities["UK"] = "Liverpool, Bristol"; // update value of UK key

        cities["USA"] = "Los Angeles, Boston"; // update value of USA key

        //cities["France"] = "Paris"; //throws run-time exception: KeyNotFoundException

​

        if(cities.ContainsKey("France")){

            cities["France"] = "Paris";

        }

        foreach(var kvp in cities)

            Console.WriteLine("Key: {0}, Value:{1}", kvp.Key, kvp.Value);

    }

}