using System;

​

public class Program {

    public static void Main(string[] args) {

        string s = "unchanged";

        StringChanger.ChangeString(s);

        Console.WriteLine("Without ref:");

        Console.WriteLine(s);

        string s2 = "unchanged";

        StringChanger2.ChangeString(ref s2);

        Console.WriteLine("With ref:");

        Console.WriteLine(s2);

    }

}

​

static class StringChanger

{

    public static void ChangeString(string str)

    {

        str = "changed";

    }

}

​

static class StringChanger2

{

    public static void ChangeString(ref string str)

    {

        str = "changed";

    }

}