Decorator in C#
Why read if you can watch?
Watch Decorator's video tutorialAttaches additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.
This structural code demonstrates the Decorator pattern which dynamically adds extra functionality to an existing object.
using System;
class MainApp
{
static void Main()
{
// Create ConcreteComponent and two Decorators
ConcreteComponent c = new ConcreteComponent();
ConcreteDecoratorA d1 = new ConcreteDecoratorA();
ConcreteDecoratorB d2 = new ConcreteDecoratorB();
// Link decorators
d1.SetComponent(c);
d2.SetComponent(d1);
d2.Operation();
// Wait for user
Console.Read();
}
}
// "Component"
abstract class Component
{
public abstract void Operation();
}
// "ConcreteComponent"
class ConcreteComponent : Component
{
public override void Operation()
{
Console.WriteLine("ConcreteComponent.Operation()");
}
}
// "Decorator"
abstract class Decorator : Component
{
protected Component component;
public void SetComponent(Component component)
{
this.component = component;
}
public override void Operation()
{
if (component != null)
{
component.Operation();
}
}
}
// "ConcreteDecoratorA"
class ConcreteDecoratorA : Decorator
{
private string addedState;
public override void Operation()
{
base.Operation();
addedState = "New State";
Console.WriteLine("ConcreteDecoratorA.Operation()");
}
}
// "ConcreteDecoratorB"
class ConcreteDecoratorB : Decorator
{
public override void Operation()
{
base.Operation();
AddedBehavior();
Console.WriteLine("ConcreteDecoratorB.Operation()");
}
void AddedBehavior()
{
}
}
ConcreteComponent.Operation()
ConcreteDecoratorA.Operation()
ConcreteDecoratorB.Operation()
