gistfile1.cs

class Song
{
    public void Sing()
    {
        Wall wall = new Wall();

        wall.Beers.Add(new Beer("Peroni"));

        foreach (Beer beer in wall.Beers)
        {
            Console.WriteLine(beer.Name);
        }
    }
}

public class Beer
{
    public string Name { get; set; }

    public Beer(string name)
    {
        Name = name;
    }
}

public class Wall
{
    public List<Beer> Beers { get; set; }
}