using System;

public class Program

{

    public static void Main()

    {

        object a = 1;

        var y = a as string;

        if(!( a is string))

        {

            Console.WriteLine("a is not string");

        }

        if( a is int)

        {

            Console.WriteLine("a is int");

        }       

        if(y == null)

        {

            Console.WriteLine("y is null");

        }

        try {

        var x = (string)a;

        }

        catch(Exception e)

        {

            Console.WriteLine("Cast crash with exception: " + e);

        }

    }

}