public static void Main(String[] args)
{
Object o1 = new Thing();
Bop b = (Bop)o1;
b.Dance();
Musician m = (Musician)o1;
m.Sing();
Musician m2 = (Musician)b;
b.Dance();
}
public static void Sing(Musician m)
{
Console.WriteLine(m.Sing());
}