In object-oriented programming, inheritance, and composition are two different ways of building relationships between classes. Inheritance allows a class to inherit properties and methods from a parent class, while composition involves building a new class by combining existing classes.

While both inheritance and composition can be used to achieve similar results, there are cases where the composition is a better choice. In this post, we’ll explore why you might prefer composition over inheritance in C#.

1. Greater Flexibility One of the main benefits of composition is that it offers greater flexibility than inheritance. With inheritance, you are limited to the properties and methods defined in the parent class. If you need to change or extend these properties or methods, you will need to modify the parent class. This can be a problem if the parent class is widely used, as changes to the class could have unforeseen consequences.

On the other hand, with composition, you can easily create new classes by combining existing classes. This means that you can create new classes without modifying the original classes. This gives you greater flexibility to adapt to changing requirements and reduces the risk of introducing bugs into existing code.

For example, let’s say you are building a game and you have a class called Enemy. The Enemy class has properties such as health, damage, and speed. You want to create a new class called BossEnemy, which has all of the properties of the Enemy class, but with some additional properties such as a special attack.

If you use inheritance, you would need to modify the Enemy class to include the new properties for the BossEnemy. This could have unintended consequences for other parts of the game that use the Enemy class. On the other hand, if you use composition, you could create a new class called BossEnemy that contains an instance of the Enemy class and adds the additional properties.

2. Better Encapsulation Another benefit of composition is that it encourages better encapsulation. Encapsulation is the idea that an object should hide its internal state from the outside world and only expose a limited set of properties and methods. This makes it easier to reason about the behavior of the object and reduces the risk of introducing bugs.

With inheritance, the child class has access to all of the properties and methods of the parent class. This can make it difficult to enforce encapsulation, as any changes to the parent class can affect the child class. On the other hand, with composition, you can define a limited set of properties and methods for the new class, which makes it easier to reason about its behavior.

For example, let’s say you are building a web application and you have a class called User. The User class has properties such as username, email, and password. You want to create a new class called PublicUser, which has all of the properties of the User class, but with the password property removed.

If you use inheritance, the PublicUser class would have access to all of the properties and methods of the User class, including the password property. This could be a security risk, as the password property should not be exposed to the outside world. On the other hand, if you use composition, you could create a new class called PublicUser that contains an instance of the User class and only exposes the username and email properties.

3. Easier Testing Another benefit of composition is that it makes it easier to test your code. When you use composition, you can easily create mock objects to test your code. Mock objects are objects that simulate the behavior of a real object, but with a simplified interface that makes it easier to test.

With inheritance, it can be difficult to create mock objects, as any changes to the parent class can affect the behavior of the child class. On the other hand, with composition, you can create mock objects for each of the component classes, which makes it

easier to test your code in isolation. This is particularly useful for testing complex systems with multiple dependencies, as it allows you to test each component in isolation and ensure that they work together correctly.

For example, let’s say you are building a financial application that processes transactions. The application has a class called TransactionProcessor, which depends on a database and a messaging system. If you use inheritance to create the TransactionProcessor class, it would be difficult to test in isolation, as any changes to the database or messaging system could affect the behavior of the TransactionProcessor class.

On the other hand, if you use composition to create the TransactionProcessor class, you could create mock objects for the database and messaging system, which would allow you to test the TransactionProcessor class in isolation.

When to use Inheritance Inheritance is useful when you have a hierarchy of classes with a shared set of properties and methods. Inheritance allows you to define these properties and methods in a parent class and then reuse them in the child classes. This can save you time and reduce code duplication.

For example, let’s say you are building a game and you have a hierarchy of classes for different types of weapons. Each type of weapon has a common set of properties and methods, such as damage, range, and reload time. In this case, it would make sense to use inheritance to define a parent class called Weapon, which contains these properties and methods.

When to use Composition Composition is useful when you need greater flexibility and encapsulation. Composition allows you to create new classes by combining existing classes, which makes it easier to adapt to changing requirements and reduces the risk of introducing bugs.

For example, let’s say you are building a web application and you have a class called User. The User class has properties such as username, email, and password. You want to create a new class called PublicUser, which has all of the properties of the User class, but with the password property removed. In this case, it would make sense to use composition to create the PublicUser class, as it allows you to define a limited set of properties and methods and enforce better encapsulation.

In conclusion, both inheritance and composition are important tools in object-oriented programming. While inheritance can be useful for defining hierarchies of classes with shared properties and methods, composition offers greater flexibility, better encapsulation, and easier testing. By understanding the strengths and weaknesses of each approach, you can choose the right tool for the job and build better software.