10.3. Inheritance

While the design of OOP inheritance can be complex, the basic idea of inheritance is to inherit fields and methods from one class to another (reusability).

To achieve inheritance, you design a base class and derived classes:

• Derived Class (child): the class that inherits from another class

• Base Class (parent): the class being inherited from

To inherit from a class, use the : symbol.

In the example below, the Car class (child) inherits the fields and methods from the Vehicle class (parent) and the Car class can access the data and actions defined in the Vehicle class: [1]

class Vehicle                               // base class (parent)
{
    public string brand = "Ford";           // Vehicle field
    public void honk()                      // Vehicle method
    {
        Console.WriteLine("Tuut, tuut!");
    }
}


class Car : Vehicle                         // derived class (child)
{
    public string modelName = "Mustang";    // Car field
}


class Program
{
    static void Main(string[] args)         // the Main method
    {
        Car myCar = new Car();              // Create a myCar object using the ""new" keyword

        myCar.honk();                       // Call the honk() method (From the Vehicle class)
                                            // on the myCar object

        Console.WriteLine(myCar.brand + " " + myCar.modelName);
                                            // Display the value of the brand field (from the Vehicle class)
                                            // and the value of the modelName from the Car class
    }
}

There are three classes in the preceding code: Vehicle, Car, and Program. You have defined a parent class Vehicle with some fields and methods. When you want to create a class Car that would share the same information and actions, instead of repeating the code, you inherit the information and actions from Vehicle. Namely, you are creating a child class Car to reuse the code from the parent class.

As you can imagine, you may reuse Vehicle by inheriting it again when you want to create similar child class such as Truck. That way, you only need to define the fields and methods once in the parent class once, and use them in all the child classes.

Footnotes

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[1]

C# Inheritance