using System;  

namespace program

{  

     public class Nullable2 

    {  

       public  static void Main(string[] args)  

        {  

            int? a = 10;  

            double? f = 10.10;    

            bool? b = false;  

            char? c = 'S';    

            if (a.HasValue)  

            {  

                Console.WriteLine(a.Value);  

            }  

            else Console.WriteLine("a contains null value");    

            a = null;  

            if (a.HasValue)  

            {  

                Console.WriteLine(a.Value);  

            }  

            else Console.WriteLine("a contains null value");  

        }  

    }  

}