using System;

public class Program

{

    class A

    {

        string name;

        public A(string name)

        {

            this.name = name;

        }

    };

    static A s = null;

    static A DoSomething(A r)

    {

        s = r;

        var res = new A("Bar");

        // 2.

        return res;

    }

    public static void Main()

    {

        var a = new A("Foo");

        // 1.

        var b = DoSomething(a);

        // 3.       

        a = null;

        // 4.

        b = null;

        // 5.       

    }

}