Arraylist method

Hi, i have a arraylist with object, i have a constructor, i will like to change some value with a method but i have a error

why the get and set not work?

using System;using System.IO;using System.Collections;  class Monde{ privatestring pays;privatestring capital;  public Monde(string pays, string capital){ this.pays = pays.ToUpper();this.capital = capital.ToUpper(); }  publicoverridestring ToString(){returnstring.Format("{0} {1}",pays, capital);} publicstring Pays{get{return pays; }set{ pays = value; }}     } class ArrayList2{     staticvoid Afficher2(ArrayList coupeSoccer, string mess){
          Console.WriteLine("Contenu de la liste des premier pays "+ mess + ":\n");for(int i = 0; i < coupeSoccer.Count; i++)
              Console.WriteLine("{0,3}) {1}", i, coupeSoccer[i]);
          Console.WriteLine("\n....\n");   } staticvoid Modifier(ArrayList maListe){ 
          maListe[0].Pays = "Montreal"; }  staticvoid Main(string[] args){  
            ArrayList maListe = new ArrayList();
            maListe.Add(new Monde("Canada", "Ottawa"));
            maListe.Add(new Monde("France", "Paris"));
            Afficher2(maListe, "Voici ma liste");
            Modifier(maListe);}}