using System;

public class Program

{

    public static void Main()

    {

        var x = new A();

        x.v1 = "aaa";

        Console.WriteLine(x.v1);

        var b = new B(x);

        Console.WriteLine(x.v1);

        Console.WriteLine(b.a.v1);

        Console.WriteLine("Alterando");

        x.v1 = "bbbb";

        Console.WriteLine(x.v1);

        Console.WriteLine(b.a.v1);

        Console.WriteLine("Alterando");

        b.a.v1 = "cccc";

        Console.WriteLine(x.v1);

        Console.WriteLine(b.a.v1);

    }

    public class A {

        public string v1 {get; set;}

        public string v2 {get; set;}

    }

    public class B {

        public B(A _a){

            a = _a;

        }

        public A a {get; set;}

    }

}