using System;

Console.WriteLine(Formater(9));

Console.WriteLine(Formater(99));

Console.WriteLine(Formater(999));

Console.WriteLine(Formater(9999));

Console.WriteLine(Formater(99999));

Console.WriteLine(Formater(999999));

Console.WriteLine(Formater(9999999));

Console.WriteLine(Formater(99999999));

​

static string Formater(int nb)

{

   string norm = "00000";

   int norml=norm.Length;

   norm += nb.ToString();

   norm=norm .Substring(nb.ToString().Length,norml);

   return norm;

}

​