Inheritance and Polymorphism

Base Method Calls

An override can call the base method and then add more behavior.

Base Method Calls

BaseMethodCalls.cs 
using System;

class Ticket
{
    public virtual string Format()
    {
        return "ticket";
    }
}

class PriorityTicket : Ticket
{
    private readonly string level;

    public PriorityTicket(string level)
    {
        this.level = level;
    }

    public override string Format()
    {
        return base.Format() + ":" + level;
    }
}

class Program
{
    static void Main()
    {
        string level = ;
        PriorityTicket ticket = new PriorityTicket(level);
        string formatted = ticket.Format();

        Console.WriteLine($"level={level}");
        Console.WriteLine($"formatted={formatted}");
    }
}

using System;

class Ticket
{
    public virtual string Format()
    {
        return "ticket";
    }
}

class PriorityTicket : Ticket
{
    private readonly string level;

    public PriorityTicket(string level)
    {
        this.level = level;
    }

    public override string Format()
    {
        return base.Format() + ":" + level;
    }
}

class Program
{
    static void Main()
    {
        string level = ;
        PriorityTicket ticket = new PriorityTicket(level);
        string formatted = ticket.Format();

        Console.WriteLine($"level={level}");
        Console.WriteLine($"formatted={formatted}");
    }
}

using System;

class Ticket
{
    public virtual string Format()
    {
        return "ticket";
    }
}

class PriorityTicket : Ticket
{
    private readonly string level;

    public PriorityTicket(string level)
    {
        this.level = level;
    }

    public override string Format()
    {
        return base.Format() + ":" + level;
    }
}

class Program
{
    static void Main()
    {
        string level = ;
        PriorityTicket ticket = new PriorityTicket(level);
        string formatted = ticket.Format();

        Console.WriteLine($"level={level}");
        Console.WriteLine($"formatted={formatted}");
    }
}
base call The `base` keyword calls a member from the base class.