ProgramDefaultGlue.cs

class Program
    {
       static IDictionary<string,int> zipCodes= new Dictionary<string,int>{
            {"Paris",75}
        };
        static IDictionary<int, int> population = new Dictionary<int, int>{
            {75,100}
        };
        
       static int? GetInterstingNumber(string cityName){
            const int TOTAL_POPULATION=123;
            int? myCityCode=null;
            try
            {
                myCityCode = zipCodes[cityName];
            }
            catch(KeyNotFoundException e)
            {
                myCityCode = null;
            }
            try
            {
                return (population[myCityCode.Value] * 100 / TOTAL_POPULATION);
            }
            catch (KeyNotFoundException e)
            {
                return null;
            }
            catch(/* .Value can produce a*/ InvalidOperationException e)
            {
                return null;
            }
            
        }
        static void Main(string[] args)
        {
          Console.WriteLine("Homs has "+getInterstingNumber("Paris")+"% of France populatin");
          
        }
    }