Method Overriding in C#

Method overriding in C# allows a derived class to provide a new implementation of a method that is already defined in its base class. It is a key feature of runtime polymorphism.

Example: Program to demonstrate Method Overriding in detail.

Dog is running.
Animal is eating.
Dog is barking.

Method Overriding Example Flow

• Animal class defines two methods: Move() (virtual) and Eat().
• Dog class inherits from Animal and overrides Move() with its own implementation.
• Bark() is a new method specific to Dog.
• Move(): executes the overridden version (Dog is running.).
• eat(): executes the base class method (Animal is eating.).
• Bark(): executes the method defined in Dog.

Keywords for Method Overrriding

In C#, three keywords are used for Method Overriding which are listed below:

1. virtual Keyword

This keyword is used in the base class to define a method that can be overridden in a derived class.

Example 1: Method overriding using virtual keyword.

Dog is running.

Explanation: The Move() method in the Animal class is marked as virtual, which allows it to be overridden in the Dog class using the override keyword.

Example 2: Method overriding using virtual and override modifiers.

Base class
Derived class

Explanation:

• The base class defines show() as virtual, which means it can be overridden.
• The derived class provides its own implementation using override.
• When obj refers to a baseClass object, the base version of show() is executed.
• When obj refers to a derived object, the overridden version is executed.

2. override keyword

This keyword is used in the derived class to provide a specific implementation of a method defined in the base class.

Example: Method overriding using override keyword.

Dog is running.

Explanation: The Move() method in the Dog class uses the override keyword to change the behavior of the Move() method defined in the Animal class.

3. Base Keyword

This method is used to access members(methods, properties or constructors) of the base class from within a derived class.

Use of Base Keyword:

• Call methods or functions of base class from derived class.
• Call constructor internally of base class at the time of inheritance.

Example 1: Method overriding using Base keyword.

Animal is moving.
Dog is running.

• The Animal class defines a virtual method Move().
• The Dog class inherits from Animal and overrides the Move() method.
• Inside the overridden method, base.Move() is used to call the parent class implementation.
• After calling the base method, the derived class adds its own behavior (Dog is running.).
• In Main(), creating a Dog object and calling Move() executes both the base method and the derived method.

Example 2: How the base Keyword specifies the calling of base-class constructor from the derived class, when derived class instances are created.

Output:

Example 3: How base keyword specifies the base-class constructor called from derived class and calling a method using the base keyword from the derived class.

Output:

Key Points

• Method overriding is possible only in derived classes. Because a method is overridden in the derived class from the base class.
• A non-virtual or a static method can’t be overridden.
• Both the override method and the virtual method must have the same access level modifier.