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public class Animal
{
public string Name;
public int Popularity;
public Animal (string name, int popularity)
{
Name = name; Popularity = popularity;
}
}
public class AnimalCollection : Collection
{
// AnimalCollection is already a fully functioning list of animals.
// No extra code is required.
}
public class Zoo // The class that will expose AnimalCollection.
{ // This would typically have additional members.
public readonly AnimalCollection Animals = new AnimalCollection();
}
class Program
{
static void Main()
{
Zoo zoo = new Zoo();
zoo.Animals.Add (new Animal ("Kangaroo", 10));
zoo.Animals.Add (new Animal ("Mr Sea Lion", 20));
foreach (Animal a in zoo.Animals) Console.WriteLine (a.Name);
}
}
As it stands, AnimalCollection is no more functional than a simple List; its
role is to provide a base for future extension. To illustrate, we’ll now add a Zoo
property to Animal, so it can reference the Zoo in which it lives and override each of
the virtual methods in Collection to maintain that property automatically:
public class Animal
{
public string Name;
public int Popularity;
public Zoo Zoo { get; internal set; }
public Animal(string name, int popularity)
{
Name = name; Popularity = popularity;
}
}
public class AnimalCollection : Collection
{
Zoo zoo;
public AnimalCollection (Zoo zoo) { this.zoo = zoo; }
Customizable Collections and Proxies | 299
Collections