//-----DECORATOR PATTERN------//

MainFile.cs

using System;

namespace Pattern_Decorator
{
class Program
{
static void Main(string[] args)
{
Beverage beverage1 = new Espresso();
Console.WriteLine("Beverage: {0}, Cost: {1}",beverage1.Description,beverage1.Cost());

Beverage beverage2 = new DarkRoast();
beverage2 = new Mocha(beverage2);
beverage2 = new Mocha(beverage2);
beverage2 = new Whip(beverage2);
Console.WriteLine("Beverage: {0}, Cost: {1}", beverage2.Description, beverage2.Cost());

Beverage beverage3 = new HouseBlend();
beverage3 = new Soy(beverage3);
beverage3 = new Mocha(beverage3);
beverage3 = new Whip(beverage3);
Console.WriteLine("Beverage: {0}, Cost: {1}", beverage3.Description, beverage3.Cost());

}
}
}


DecoratorClass.cs

using System;

namespace Pattern_Decorator
{
public abstract class Beverage
{
string description = "Unknown Beverage";
public abstract double Cost();
public string Description
{
get
{
return description;
}
set
{
description = value;
}
}
}

public abstract class CondimentDecorator : Beverage
{
}

#region Beverages

public class Espresso : Beverage
{

public Espresso()
{
Description = "Espresso";
}
public override double Cost()
{
return 1.99;
}
}

public class HouseBlend : Beverage
{

public HouseBlend()
{
Description = "HouseBlend";
}
public override double Cost()
{
return 0.89;
}
}

public class DarkRoast : Beverage
{

public DarkRoast()
{
Description = "DarkRoast";
}
public override double Cost()
{
return 2.50;
}
}

public class Decaf : Beverage
{

public Decaf()
{
Description = "Decaf";
}
public override double Cost()
{
return 2.00;
}
}

#endregion

#region Condiments

public class Mocha : CondimentDecorator
{
Beverage beverage;
public Mocha(Beverage beverage)
{
this.beverage = beverage;
Description = this.beverage.Description + ", Mocha";
}
public override double Cost()
{
return this.beverage.Cost() + 0.50;
}
}

public class Soy : CondimentDecorator
{
Beverage beverage;
public Soy(Beverage beverage)
{
this.beverage = beverage;
Description = this.beverage.Description + ", Soy";
}
public override double Cost()
{
return this.beverage.Cost() + 1.50;
}
}

public class Whip : CondimentDecorator
{
Beverage beverage;
public Whip(Beverage beverage)
{
this.beverage = beverage;
Description = this.beverage.Description + ", Whip";
}
public override double Cost()
{
return this.beverage.Cost() + 0.10;
}
}

#endregion

}