using System;

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public class Person

{

    public Int32 Age { get; set; }

    public static void ChangeAge(Int32 age) { age = 10; }

    public static void ChangeAge(ref Int32 age) { age = 20; }

    public static void ChangeAge(Person person) { person.Age = 30; }

    public static void ChangeAge(ref Person person) { person.Age = 40; }

    public static void DeletePerson(Person person) { person = null; }

    public static void DeletePerson(ref Person person) { person = null; }

    public void Main()

    {

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        Int32 newAge = 0;

        Person bob;

​

        bob = new Person();

        bob.Age = 5;

        Console.WriteLine(bob);

        Person.ChangeAge(bob);

        // how old is bob now? 30

        Console.WriteLine(bob.Age);

        bob = new Person();

        bob.Age = 5;

        Console.WriteLine(bob);

        Person.ChangeAge(ref bob);

        // how old is bob now? 40

        Console.WriteLine(bob.Age);

    }

​

}

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