using System;

namespace _10AbstractClasses

{

//ABSTRACT CLASSES

//Abstract classes serve a similar purpose as interfaces: they allow us to have

//multiple classes inherit a set of methods, properties, and other members.

//An abstract class is defined using the *abstract* keyword.

public abstract class Basic

{

//Members go here

}

//Methods in an abstract class can also be marked with the *abstract* keyword.

//Such methods must not have an implementation, because the implementation

//will be provided by the inheriting class.

//Unlike interfaces, abstract classes may also have concrete methods with an implementation.

public abstract class Gem

{

public abstract decimal GetValuePerCarat(); //Abstract method

public string GetCommonColors() //Concrete method

{

return "Clear, Purple, Red, Black, White";

}

}

//We can have other classes inherit from our abstract base class.

//Extra special bonus points to whomever knows what these class names are from.

public class Garnet : Gem

{

public override decimal GetValuePerCarat()

{

return 500M;

}

}

public class Amethyst : Gem

{

public override decimal GetValuePerCarat()

{

return 300M;

}

}

public class Pearl : Gem

{

public override decimal GetValuePerCarat()

{

return 400M;

}

}

//If our derived class does not implement an abstract method, we get

//a compilation error.

//Uncomment the below class to see this.

//public class Peridot : Gem { }

//ABSTRACT PROPERTIES

//Properties in a class can also be marked abstract. The inheriting class

//can then override the properties to provide their own implementation.

public abstract class Mineral //Base class

{

public abstract double Hardness { get; }

}

public class Quartz : Mineral //Derived class

{

public override double Hardness

{

get { return 7.0; }

}

}

public class Bismuth : Mineral //Derived class

{

public override double Hardness

{

get { return 2.25; }

}

}

class Program

{

static void Main(string[] args)

{

Console.WriteLine("-----------------Abstract Basics--------------------");

var garnet = new Garnet();

var value = garnet.GetValuePerCarat(); //Defined in Garnet class

Console.WriteLine("Garnet value per carat: " + value);

var commonColors = garnet.GetCommonColors(); //Defined in Gem base class

Console.WriteLine("All gems common colors: " + commonColors);

//OTHER DETAILS

//Like an interface, abstract classes cannot be instantiated directly.

//If you uncomment the below line, you will get a compilation error.

//var myGem = new Gem();

//Also, because of polymorphism, an instance of a class derived from an abstract

//can be treated as an instance of that abstract class.

Mineral myMineral = new Bismuth();

var hardness = myMineral.Hardness;

}

}

}

//Go look at the Notes.cs file for additional information.