Inheritance and Polymorphism

Method Overriding

A derived class can override a virtual method from its base class.

Method Overriding

MethodOverriding.cs 
using System;

class Notifier
{
    public virtual string Message()
    {
        return "notice";
    }
}

class EmailNotifier : Notifier
{
    private readonly string subject;

    public EmailNotifier(string subject)
    {
        this.subject = subject;
    }

    public override string Message()
    {
        return "email:" + subject;
    }
}

class Program
{
    static void Main()
    {
        string subject = ;
        EmailNotifier notifier = new EmailNotifier(subject);
        string message = notifier.Message();

        Console.WriteLine($"subject={subject}");
        Console.WriteLine($"message={message}");
    }
}

using System;

class Notifier
{
    public virtual string Message()
    {
        return "notice";
    }
}

class EmailNotifier : Notifier
{
    private readonly string subject;

    public EmailNotifier(string subject)
    {
        this.subject = subject;
    }

    public override string Message()
    {
        return "email:" + subject;
    }
}

class Program
{
    static void Main()
    {
        string subject = ;
        EmailNotifier notifier = new EmailNotifier(subject);
        string message = notifier.Message();

        Console.WriteLine($"subject={subject}");
        Console.WriteLine($"message={message}");
    }
}

using System;

class Notifier
{
    public virtual string Message()
    {
        return "notice";
    }
}

class EmailNotifier : Notifier
{
    private readonly string subject;

    public EmailNotifier(string subject)
    {
        this.subject = subject;
    }

    public override string Message()
    {
        return "email:" + subject;
    }
}

class Program
{
    static void Main()
    {
        string subject = ;
        EmailNotifier notifier = new EmailNotifier(subject);
        string message = notifier.Message();

        Console.WriteLine($"subject={subject}");
        Console.WriteLine($"message={message}");
    }
}
override An override replaces virtual base behavior for a derived class.