/*
A Programmer's Introduction to C# (Second Edition)
by Eric Gunnerson
Publisher: Apress L.P.
ISBN: 1-893115-62-3
*/
// 01 - Object-Oriented BasicsPolymorphism and Virtual Functions
// copyright 2000 Eric Gunnerson
using System;
public PolymorphismVirtualFunctions
{
public static void CallPlay(MusicServer ms)
{
ms.Play();
}
public static void Main()
{
MusicServer ms = new WinAmpServer();
CallPlay(ms);
ms = new MediaServer();
CallPlay(ms);
}
}
public abstract class MusicServer
{
public abstract void Play();
}
public class WinAmpServer: MusicServer
{
public override void Play()
{
Console.WriteLine("WinAmpServer.Play()");
}
}
public class MediaServer: MusicServer
{
public override void Play()
{
Console.WriteLine("MediaServer.Play()");
}
}
Class Interface
Method override 3
/*
Learning C#
by Jesse Liberty
Publisher: O'Reilly
ISBN: 0596003765
*/
using System;
class Dog
{
private int weight;
// constructor
public Dog(int weight)
{
this.weight = weight;
}
// override Object.ToString
public override string ToString()
{
return weight.ToString();
}
}
public class TesterOverride
{
static void Main()
{
int i = 5;
Console.WriteLine("The value of i is: {0}", i.ToString());
Dog milo = new Dog(62);
Console.WriteLine("My dog Milo weighs {0} pounds", milo.ToString());
}
}
Demonstrates the use of a virtual property to override a base class property
/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa
Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
//
// VProp.cs -- Demonstrates the use of a virtual method to override
// a base class method.
//
// Compile this program with the following command line:
// C:>csc VProp.cs
namespace nsVirtual
{
using System;
public class VPropclsMain
{
static public void Main ()
{
clsBase Base = new clsBase();
clsFirst First = new clsFirst();
Base.SetString ("This should set the base class property");
First.SetString ("This should set the derived class property");
Console.WriteLine();
Console.WriteLine (Base.GetString());
Console.WriteLine (First.GetString());
}
}
class clsBase
{
public void SetString (string str)
{
StrProp = str;
}
public string GetString ()
{
return (StrProp);
}
virtual protected string StrProp
{
get
{
Console.WriteLine ("Getting Base string");
return (m_BaseString);
}
set
{
Console.WriteLine ("Setting Base string");
m_BaseString = value;
}
}
private string m_BaseString = "";
}
class clsFirst : clsBase
{
override protected string StrProp
{
get
{
Console.WriteLine ("Getting derived string");
return (m_DerivedString);
}
set
{
Console.WriteLine ("Setting derived string");
m_DerivedString = value;
}
}
private string m_DerivedString = "";
}
}
Demonstrates the use of a virtual method to override a base class method
/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa
Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
//
// Virtual.cs -- Demonstrates the use of a virtual method to override
// a base class method.
//
// Compile this program with the following command line:
// C:>csc Virtual.cs
namespace nsVirtual
{
using System;
public class VirtualclsMain
{
static public void Main ()
{
clsBase Base = new clsBase();
clsFirst First = new clsFirst();
clsSecond Second = new clsSecond();
Base.Show();
First.Show();
Second.Show ();
}
}
class clsBase
{
public void Show ()
{
Describe ();
}
virtual protected void Describe ()
{
Console.WriteLine ("Called the base class Describe() method");
}
}
class clsFirst : clsBase
{
override protected void Describe ()
{
Console.WriteLine ("Called the derived class Describe() method");
}
}
class clsSecond : clsBase
{
}
}
illustrates polymorphism
/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy
Publisher: Sybex;
ISBN: 0782129110
*/
/*
Example7_2.cs illustrates polymorphism
*/
using System;
// declare the MotorVehicle class
class MotorVehicle
{
// declare the fields
public string make;
public string model;
// define a constructor
public MotorVehicle(string make, string model)
{
this.make = make;
this.model = model;
}
// define the Accelerate() method (may be overridden in a
// derived class)
public virtual void Accelerate()
{
Console.WriteLine(model + " accelerating");
}
}
// declare the Car class (derived from MotorVehicle)
class Car : MotorVehicle
{
// define a constructor
public Car(string make, string model) :
base(make, model)
{
// do nothing
}
// override the base class Accelerate() method
public override void Accelerate()
{
Console.WriteLine("Pushing gas pedal of " + model);
base.Accelerate(); // calls the Accelerate() method in the base class
}
}
// declare the Motorcycle class (derived from MotorVehicle)
class Motorcycle : MotorVehicle
{
// define a constructor
public Motorcycle(string make, string model) :
base(make, model)
{
// do nothing
}
// override the base class Accelerate() method
public override void Accelerate()
{
Console.WriteLine("Twisting throttle of " + model);
base.Accelerate(); // calls the Accelerate() method in the base class
}
}
public class Example7_2
{
public static void Main()
{
// create a Car object and call the object's Accelerate() method
Car myCar = new Car("Toyota", "MR2");
myCar.Accelerate();
// create a Motorcycle object and call the object's Accelerate() method
Motorcycle myMotorcycle = new Motorcycle("Harley-Davidson", "V-Rod");
myMotorcycle.Accelerate();
}
}
When a virtual method is not overridden, the base class method is used
/*
C#: The Complete Reference
by Herbert Schildt
Publisher: Osborne/McGraw-Hill (March 8, 2002)
ISBN: 0072134852
*/
/* When a virtual method is not overridden,
the base class method is used. */
using System;
class Base {
// Create virtual method in the base class.
public virtual void who() {
Console.WriteLine("who() in Base");
}
}
class Derived1 : Base {
// Override who() in a derived class.
public override void who() {
Console.WriteLine("who() in Derived1");
}
}
class Derived2 : Base {
// This class does not override who().
}
public class NoOverrideDemo {
public static void Main() {
Base baseOb = new Base();
Derived1 dOb1 = new Derived1();
Derived2 dOb2 = new Derived2();
Base baseRef; // a base-class reference
baseRef = baseOb;
baseRef.who();
baseRef = dOb1;
baseRef.who();
baseRef = dOb2;
baseRef.who(); // calls Base's who()
}
}
Demonstrate a virtual method
/*
C#: The Complete Reference
by Herbert Schildt
Publisher: Osborne/McGraw-Hill (March 8, 2002)
ISBN: 0072134852
*/
// Demonstrate a virtual method.
using System;
class Base {
// Create virtual method in the base class.
public virtual void who() {
Console.WriteLine("who() in Base");
}
}
class Derived1 : Base {
// Override who() in a derived class.
public override void who() {
Console.WriteLine("who() in Derived1");
}
}
class Derived2 : Base {
// Override who() again in another derived class.
public override void who() {
Console.WriteLine("who() in Derived2");
}
}
public class OverrideDemo {
public static void Main() {
Base baseOb = new Base();
Derived1 dOb1 = new Derived1();
Derived2 dOb2 = new Derived2();
Base baseRef; // a base-class reference
baseRef = baseOb;
baseRef.who();
baseRef = dOb1;
baseRef.who();
baseRef = dOb2;
baseRef.who();
}
}