Method Overriding in C#

This article explains method overriding and its various applications using examples in C#.

Method Overriding

Overriding can be defined as: being able to change or augment the behavior of methods in classes, known as overriding their logic; it is one of the most powerful aspects of Object Oriented Programming.

Explanation

Suppose you have a Phone, no please don’t suppose everyone has a phone today, although some people even have more than one. Okay leave it, so if you have phone:

Then there must be ring facility in it:

Now your phone can be of any type, like it can be cellular, satellite or landline, these all types of phones will also have the same or a different functionality (based on their attribute).

Now whenever you receive a call, the caller doesn’t know whether you have a cellular phone, landline phone or anything else, he/she just calls you and according to that call operation your phone rings. In the case of method overriding, your phone works as a class and the ring is the functionality.

Keywords in Method Overriding

There are the following 3 types of keywords used in C# for method overriding:

Virtual Keyword

It tells the compiler that this method can be overridden by derived classes.

public virtual int myValue()  
{  
    -  
    -  
    -  
}

Override Keyword

In the subclass, it tells the compiler that this method is overriding the same named method in the base class.

public override int myValue()  
{  
     -  
     -  
     -  
}

Base Keyword

In the subclass, it calls the base class method for overriding functionality.

base.myValue(); 

Method Overriding Example

using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Text;  
namespace Hello_Word  
{  
    class baseClass  
    {  
        public virtual void Greetings()  
        {  
            Console.WriteLine("baseClass Saying Hello!");  
        }  
    }  
    class subClass : baseClass  
    {  
        public override void Greetings()  
        {  
            base.Greetings();  
            Console.WriteLine("subClass Saying Hello!");  
        }  
    }  
    class Program  
    {  
        static void Main(string[] args)  
        {  
            baseClass obj1 = new subClass();  
            obj1.Greetings();  
            Console.ReadLine();  
        }  
    }  
}

An output window is showing that baseClass will get called first and then subclass. If we make certain changes in this code like:

base.Greetings();  
Console.WriteLine("subClass Saying Hello!"); // current scenario 

After making a few modifications as in the following:

Console.WriteLine("subClass Saying Hello!");  
base.Greetings(); // after modifications

Now our output will be like this:

If we remove "base.Greetings();" then the compiler will not call the baseclass as in the following:

using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Text;  
namespace Hello_Word  
{  
    class baseClass  
    {  
        public virtual void Greetings()  
        {  
            Console.WriteLine("baseClass Saying Hello!");  
        }  
    }  
    class subClass : baseClass  
    {  
        public override void Greetings()  
        {  
            Console.WriteLine("subClass Saying Hello!");  
            // base.Greetings();  
        }  
    }  
    class Program  
    {  
        static void Main(string[] args)  
        {  
            baseClass obj1 = new subClass();  
            obj1.Greetings();  
            Console.ReadLine();  
        }  
    }  
}

Now making some other changes, like placing:

baseClass obj1 = new baseClass();  
obj1.Greetings();

Instead of:

baseClass obj1 = new subClass();  
obj1.Greetings(); 

Now let’s check the output window, what’s its showing now:

So as you are seeing that now its calling only the baseClass. So now I guess you will be a little closer to the method overriding functionality.