Creational Design Patterns in C#: Building Flexible and Scalable Software by Vaskaran Sarcar

Author:Vaskaran Sarcar
Language: eng
Format: mobi
ISBN: 9798868815676
Publisher: Apress
Published: 2025-07-15T00:00:00+00:00

PRIMARY CONSTRUCTOR MAKES THE CODE CONCISE

Using the Primary constructor (introduced in C#12) and removing the _type field, you can make the Car class concise as follows:

#region The code segment that uses a primary constructor

class Car(string type)

{

/*

* You can use any data structure that you prefer.

* I have used LinkedList<String> in this case.

*/

private LinkedList<string> _parts = new();

// There are no other changes in the remaining code

#endregion

You can make similar changes in equivalent code as well. I showed you the code with and without primary constructors to make you familiar with both approaches. Sometimes I avoid writing code that is very specific to the C# programming language because many C# developers are Java developers as well. In fact, the preface of the classical GoF book says that the design patterns require neither unusual language features nor amazing programming tricks with which to astound your friends and managers. However, you can have a different thought. So, you can choose the approach that serves you best.

Typically, a builder interface is needed for creating parts of a Product object. In our example, Builder is an abstract class that plays this role. It contains the methods to build different parts of a product.

In this example, you see an empty method, called AddExhaustSystem, in the Builder class. Why? Ideally, this class should define all possible methods to build various parts of a product (in our example, a car). We can assume that an electric car does not need an exhaust emission system, whereas a traditional car must have such a component. I could make other methods in the Builder class empty as well; however, I forced the concrete builders to implement those methods.

There is another method, called GetCar, in this class. This method retrieves the product once the parts are assembled. Let’s have a look at this class now:

abstract class Builder

{

public abstract void SetMotor();

public abstract void InsertWheels();

public abstract void SetHeadlights();

// The exhaust emissions system is needed for regular cars

public virtual void AddExhaustSystem() { }

// To retrieve the constructed product.

public abstract Car GetCar();

}

In the upcoming examples, the TraditionalCarBuilder and ElectricCarBuilder classes make the traditional cars and electric cars, respectively. In other words, these are the concrete builders that build the internal representations of a Car instance. First, see the ElectricCarBuilder class:

// The ElectricCarBuilder builds electric cars.

class ElectricCarBuilder : Builder

{

private readonly Car _car;

public ElectricCarBuilder()

{

_car = new("electric");

}

public override void SetMotor()

{

_car.Motor = "electric motors and batteries";

_car.Add($"The {_car.Motor} are added.");

}

public override void InsertWheels()

{

_car.Wheels = 4;

_car.Add($"{_car.Wheels} wheels are added to the car.");

}

public override void SetHeadlights()

{

_car.HeadLights = 2;

_car.Add($"{_car.HeadLights} headlights are set.");

}

// NOTE: The electric car does not need the exhaust

// emission system. So, we do not need to override the base

// class method.

// Retrieve the constructed car

public override Car GetCar()

{

return _car;

}

}

Now see the TraditionalCarBuilder class (notice that it overrides the AddExhaustSystem method as well):

// The TraditionalCarBuilder builds traditional cars.

class TraditionalCarBuilder : Builder

{

private readonly Car _car;

public TraditionalCarBuilder()

{

_car = new("traditional");

}

public override void SetMotor()

{

_car.Motor = "internal combustion engine (fueled by diesel)";

_car.Add($"The {_car.Motor} is added.");

}

public override void InsertWheels()

{

_car.Wheels = 6;

_car.Add($"{_car.Wheels} wheels are added to the car.");

}

public override void SetHeadlights()

{

_car.

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