class Program
    {
        static void IncrementAge(ref Person person)
        {
            Console.WriteLine($"Inside function => {person.Name}'s age before change: {person.Age}");
            person.Age += 1;
            Console.WriteLine($"Inside function => {person.Name}'s age after change: {person.Age}");
            person = null;
        }

        static void Main(string[] args)
        {
            var alice = new Person { Name = "Alice", Age = 17 };
            Console.WriteLine($"Inside main => {alice.Name}'s age before function call: {alice.Age}");
            IncrementAge(ref alice);
            if (alice != null)
            {
                Console.WriteLine($"Inside main => {alice.Name}'s age after function call: {alice.Age}");
            }
            else
            {
                Console.WriteLine($"Inside main => Object reference not set to an instance of an object");
            }

            Console.ReadLine();
        }
    }