public static void Main()
{
ICoffeeBar first = new CoffeeBar();
ICoffeeBar second = new FancyCoffeeBar();
first.Brew(1);
second.Brew(1);
}
public static void Main()
{
CoffeeBar first = new CoffeeBar();
FancyCoffeeBar second = new FancyCoffeeBar();
// Case #1 - Can not call extension on concrete type that does not override
// coffee_do_not_work.cs(34,10): error CS1061: 'CoffeeBar' does not contain a definition for 'Brew' and no extension method 'Brew' accepting a first argument of type 'CoffeeBar' could be found (are you missing a using directive or an assembly reference?)
first.Brew(1);
// Case #1.1 - However, you can call it on a type that overrides ?!
second.Brew(1);
// Case 1.2 - You can also use this ugly cast
((ICoffeeBar)first).Brew(1);
}