Editing Decorator pattern (section)

===C#===

<syntaxhighlight lang="csharp">
namespace WikiDesignPatterns;

public interface IBike
{
    string GetDetails();
    double GetPrice();
}

public class AluminiumBike : IBike
{
    public double GetPrice() =>
        100.0;

    public string GetDetails() =>
        "Aluminium Bike";
}

public class CarbonBike : IBike
{
    public double GetPrice() =>
        1000.0;

    public string GetDetails() =>
        "Carbon";
}


public abstract class BikeAccessories : IBike
{
    private readonly IBike _bike;

    public BikeAccessories(IBike bike)
    {
        _bike = bike;
    }

    public virtual double GetPrice() =>
        _bike.GetPrice();

    public virtual string GetDetails() =>
        _bike.GetDetails();
}

public class SecurityPackage : BikeAccessories
{
    public SecurityPackage(IBike bike) : base(bike)
    {

    }

    public override string GetDetails() =>
        base.GetDetails() + " + Security Package";

    public override double GetPrice() =>
        base.GetPrice() + 1;
}

public class SportPackage : BikeAccessories
{
    public SportPackage(IBike bike) : base(bike)
    {

    }

    public override string GetDetails() =>
        base.GetDetails() + " + Sport Package";

    public override double GetPrice() =>
        base.GetPrice() + 10;
}

public class BikeShop
{
    public static void UpgradeBike()
    {
        var basicBike = new AluminiumBike();
        BikeAccessories upgraded = new SportPackage(basicBike);
        upgraded = new SecurityPackage(upgraded);

        Console.WriteLine($"Bike: '{upgraded.GetDetails()}' Cost: {upgraded.GetPrice()}");
    }
}
</syntaxhighlight>

Output:
<pre>
Bike: 'Aluminium Bike + Sport Package + Security Package' Cost: 111
</pre>