Derived Classes

A derived class can add members while keeping inherited members.

DerivedClasses.cs

using System;

class Member
{
    public string Name { get; set; } = "";
}

class PremiumMember : Member
{
    public int BonusPoints { get; set; }
}

class Program
{
    static void Main()
    {
        int bonus = ;
        PremiumMember member = new PremiumMember();
        member.Name = "Ari";
        member.BonusPoints = bonus;
        string summary = member.Name + ":" + member.BonusPoints;

        Console.WriteLine($"bonus={bonus}");
        Console.WriteLine($"summary={summary}");
    }
}

using System;

class Member
{
    public string Name { get; set; } = "";
}

class PremiumMember : Member
{
    public int BonusPoints { get; set; }
}

class Program
{
    static void Main()
    {
        int bonus = ;
        PremiumMember member = new PremiumMember();
        member.Name = "Ari";
        member.BonusPoints = bonus;
        string summary = member.Name + ":" + member.BonusPoints;

        Console.WriteLine($"bonus={bonus}");
        Console.WriteLine($"summary={summary}");
    }
}

using System;

class Member
{
    public string Name { get; set; } = "";
}

class PremiumMember : Member
{
    public int BonusPoints { get; set; }
}

class Program
{
    static void Main()
    {
        int bonus = ;
        PremiumMember member = new PremiumMember();
        member.Name = "Ari";
        member.BonusPoints = bonus;
        string summary = member.Name + ":" + member.BonusPoints;

        Console.WriteLine($"bonus={bonus}");
        Console.WriteLine($"summary={summary}");
    }
}

derived class A derived class extends a base class with more state or behavior.