comparison between value and reference in csharp

result.txt

Java
------------
Java
------------
Perl
------------
Perl
Ruby
------------
Perl
Ruby
Python
------------

value_vs_reference.cs

using System;
using System.Collections;
using System.Collections.Generic;
using static System.Console;

class Test {
    public static void Main(string[] args) {
        var list = new List<string>();

        list.Add("Java");
        Show(list);

        AddPHP(list);
        Show(list);

        AddPerl(ref list);
        Show(list);

        AddRuby(list);
        Show(list);

        AddPython(ref list);
        Show(list);
    }

    static void AddPHP(List<String> list) {
        list = new List<string>();
        list.Add("PHP");
    }

    static void AddPerl(ref List<String> list) {
        list = new List<string>();
        list.Add("Perl");
    }

    static void AddRuby(List<String> list) => list.Add("Ruby");
    static void AddPython(ref List<String> list) => list.Add("Python");

    static void Show(IEnumerable<string> ss) {
        foreach (var s in ss) WriteLine(s);
        WriteLine("------------");
    }
}