using System;

namespace Test
{
    class Person { }

    class Student : Person { }

    class MainClass
    {
        public static void Main(string[] args)
        {
            Student student = new Student();
            Person studentAsPerson = student;
            Person justPerson = new Person();

            if (student is Student)
            {
                Console.WriteLine("This instance is subclass/class of Student");
            }

            if (studentAsPerson is Student)
            {
                // This will set 's' to null if studentAsPerson is not subclass/class of Student!
                var s = studentAsPerson as Student;

                // This will throw error if studentAsPerson is not subclass/class of Student!
                var st = (Student)studentAsPerson;
                Console.WriteLine("This instance is subclass/class Student");
            }

            if (student is Person)
            {
                Console.WriteLine("This instance is subckass/class of Person");
            }

            if (studentAsPerson is Person)
            {
                Console.WriteLine("This instance is subclass/class of Person");
            }

            if (studentAsPerson.GetType() == typeof(Student))
            {
                Console.WriteLine("This object is instance of class Student!");
            }

            if (justPerson is Student) //false
            {
                Console.WriteLine("Hell no!");
            }

            if ((justPerson as Student) == null) // person is not subclass of student!
            {
                Console.WriteLine("Cannot convert person to student!");
            }
        }
    }
}