Virtual and overload

Posted on February 11, 2011June 27, 2015 by coder


   

/*
 * C# Programmers Pocket Consultant
 * Author: Gregory S. MacBeth
 * Email: gmacbeth@comporium.net
 * Create Date: June 27, 2003
 * Last Modified Date:
 */
using System;

namespace Client.Chapter_5___Building_Your_Own_Classes
{
  public class MyMainClass12 {
    static void Main(string[] args)
    {
      //The function called is based
      //upon the type called by new.
      B MyB = new C();
      D MyD = new D();

      MyB.Display();    //Calls C Display
      MyD.Display();    //Calls D Display
    }
  }
  public interface A
  {
    void Display();
  }
  class B: A
  {
    public virtual void Display()
    {
      Console.WriteLine("Class B&#039;s Display Method");
    }
  }
  class C: B
  {
    public override void Display()
    {
      Console.WriteLine("Class C&#039;s Display Method");
    }
  }
  class D: C
  {
    public override void Display()
    {
      Console.WriteLine("Class D&#039;s Display Method");
    }
  }

}

Virtual keyword can be used to start a new inheritance ladder

Posted on February 11, 2011June 27, 2015 by coder

   
 

using System;

public class Class1 {
    public static void Main(string[] strings) {
        BankAccount ba = new BankAccount();
        Test1(ba);

        SavingsAccount sa = new SavingsAccount();
        Test1(sa);
        Test2(sa);

        SpecialSaleAccount ssa = new SpecialSaleAccount();
        Test1(ssa);
        Test2(ssa);
        Test3(ssa);

        SaleSpecialCustomer ssc = new SaleSpecialCustomer();
        Test1(ssc);
        Test2(ssc);
        Test3(ssc);
        Test4(ssc);
    }

    public static void Test1(BankAccount account) {
        Console.Write("to Test(BankAccount)");
        account.Withdrawal(100);
    }

    public static void Test2(SavingsAccount account) {
        Console.Write("to Test(SavingsAccount)");
        account.Withdrawal(100);
    }

    public static void Test3(SpecialSaleAccount account) {
        Console.Write("to Test(SpecialSaleAccount)");
        account.Withdrawal(100);
    }

    public static void Test4(SaleSpecialCustomer account) {
        Console.Write("to Test(SaleSpecialCustomer)");
        account.Withdrawal(100);
    }
}

public class BankAccount {
    virtual public void Withdrawal(double dWithdrawal) {
        Console.WriteLine(" invokes BankAccount.Withdrawal()");
    }
}

public class SavingsAccount : BankAccount {
    override public void Withdrawal(double dWithdrawal) {
        Console.WriteLine(" invokes SavingsAccount.Withdrawal()");
    }
}
public class SpecialSaleAccount : SavingsAccount {
    new virtual public void Withdrawal(double dWithdrawal) {
        Console.WriteLine(" invokes SpecialSaleAccount.Withdrawal()");
    }
}

public class SaleSpecialCustomer : SpecialSaleAccount {
    override public void Withdrawal(double dWithdrawal) {
        Console.WriteLine
          (" invokes SaleSpecialCustomer.Withdrawal()");
    }
}

Polymorphism

Posted on February 11, 2011June 27, 2015 by coder

   
 


using System;

public class MotorVehicle {
    public string make;
    public string model;

    public MotorVehicle(string make, string model) {
        this.make = make;
        this.model = model;
    }

    public virtual void Accelerate() {
        Console.WriteLine(model + " accelerating");
    }

}
public class Product : MotorVehicle {
    public Product(string make, string model) :
        base(make, model) {
    }
    public override void Accelerate() {
        Console.WriteLine("Pushing gas pedal of " + model);
        base.Accelerate();
    }

}
public class Motorcycle : MotorVehicle {
    public Motorcycle(string make, string model) :
        base(make, model) {
        // do nothing
    }

    public override void Accelerate() {
        Console.WriteLine("Twisting throttle of " + model);
        base.Accelerate();
    }

}


class MainClass {

    public static void Main() {
        Product myProduct = new Product("Toyota", "MR2");
        myProduct.Accelerate();

        Motorcycle myMotorcycle =
          new Motorcycle("Harley-Davidson", "V-Rod");
        myMotorcycle.Accelerate();

    }

}

Illustrates method overloading

Posted on February 11, 2011June 27, 2015 by coder


   

/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy

Publisher: Sybex;
ISBN: 0782129110
*/

/*
  Example5_9.cs illustrates method overloading
*/


// declare the Swapper class
class Swapper
{

  // this Swap() method swaps two int parameters
  public void Swap(ref int x, ref int y)
  {
    int temp = x;
    x = y;
    y = temp;
  }

  // this Swap() method swaps two float parameters
  public void Swap(ref float x, ref float y)
  {
    float temp = x;
    x = y;
    y = temp;
  }

}


public class Example5_9
{

  public static void Main()
  {

    // create a Swapper object
    Swapper mySwapper = new Swapper();

    // declare two int variables
    int intValue1 = 2;
    int intValue2 = 5;
    System.Console.WriteLine("initial intValue1 = " + intValue1 +
      ", intValue2 = " + intValue2);

    // swap the two float variables
    // (uses the Swap() method that accepts int parameters)
    mySwapper.Swap(ref intValue1, ref intValue2);

    // display the final values
    System.Console.WriteLine("final   intValue1 = " + intValue1 +
      ", intValue2 = " + intValue2);

    // declare two float variables
    float floatValue1 = 2f;
    float floatValue2 = 5f;
    System.Console.WriteLine("initial floatValue1 = " + floatValue1 +
      ", floatValue2 = " + floatValue2);

    // swap the two float variables
    // (uses the Swap() method that accepts float parameters)
    mySwapper.Swap(ref floatValue1, ref floatValue2);

    // display the final values
    System.Console.WriteLine("final   floatValue1 = " + floatValue1 +
      ", floatValue2 = " + floatValue2);
    mySwapper.Swap(ref floatValue1, ref floatValue2);

  }

}

Operator Overloading

Posted on February 11, 2011June 27, 2015 by coder

   
 

using System;


public class Rectangle {
    public int width;
    public int height;

    public Rectangle(int width, int height) {
        this.width = width;
        this.height = height;
    }

    public override string ToString() {
        return "width = " + width + ", height = " + height;
    }

    public static bool operator ==(Rectangle lhs, Rectangle rhs) {
        Console.WriteLine("In operator ==");
        if (lhs.width == rhs.width &amp;&amp; lhs.height == rhs.height) {
            return true;
        } else {
            return false;
        }
    }

    public static bool operator !=(Rectangle lhs, Rectangle rhs) {
        Console.WriteLine("In operator !=");
        return !(lhs == rhs);
    }

    public override bool Equals(object obj) {
        Console.WriteLine("In Equals()");
        if (!(obj is Rectangle)) {
            return false;
        } else {
            return this == (Rectangle)obj;
        }
    }

    public static Rectangle operator +(Rectangle lhs, Rectangle rhs) {
        Console.WriteLine("In operator +");
        return new Rectangle(
          lhs.width + rhs.width, lhs.height + rhs.height);
    }

}
class MainClass {

    public static void Main() {

        Rectangle myRectangle = new Rectangle(1, 4);
        Console.WriteLine("myRectangle: " + myRectangle);
        Rectangle myRectangle2 = new Rectangle(1, 4);
        Console.WriteLine("myRectangle2: " + myRectangle2);

        if (myRectangle == myRectangle2) {
            Console.WriteLine(
              "myRectangle is equal to myRectangle2");
        } else {
            Console.WriteLine(
              "myRectangle is not equal to myRectangle2");
        }

        Rectangle myRectangle3 = myRectangle + myRectangle2;
        Console.WriteLine("myRectangle3: " + myRectangle3);
    }
}

Overloaded methods with identical signatures cause compilation errors, even if return types are different.

Posted on February 11, 2011June 27, 2015 by coder

   




public class MethodOverloadError
{
   public int Square( int x )
   {
      return x * x;
   }
   public double Square( int y )
   {
      return y * y;
   }
}

Sorting and Searching:Overloading Relational Operators

Posted on February 11, 2011June 27, 2015 by coder


   

/*
A Programmer&#039;s Introduction to C# (Second Edition)
by Eric Gunnerson

Publisher: Apress  L.P.
ISBN: 1-893115-62-3
*/

// 28 - System.Array and the Collection ClassesSorting and SearchingOverloading Relational Operators
// copyright 2000 Eric Gunnerson
using System;

public class OverloadingRelationalOperators
{
    public static void Main()
    {
        Employee george = new Employee("George", 1);
        Employee fred = new Employee("Fred", 2);
        Employee tom = new Employee("Tom", 4);
        Employee bob = new Employee("Bob", 3);
        
        Console.WriteLine("George < Fred: {0}", george < fred);
        Console.WriteLine("Tom >= Bob: {0}", tom >= bob);
    }
} 
public class Employee: IComparable
{
    public Employee(string name, int id)
    {
        this.name = name;
        this.id = id;
    }
    
    int IComparable.CompareTo(object obj)
    {
        Employee emp2 = (Employee) obj;
        if (this.id > emp2.id)
        return(1);
        if (this.id < emp2.id)
        return(-1);
        else
        return(0);
    }
    public static bool operator <(
    Employee emp1,
    Employee emp2)
    {
        IComparable    icomp = (IComparable) emp1;
        return(icomp.CompareTo (emp2) < 0);
    }
    public static bool operator >(
    Employee emp1,
    Employee emp2)
    {
        IComparable    icomp = (IComparable) emp1;
        return(icomp.CompareTo (emp2) > 0);
    }
    public static bool operator <=(
    Employee emp1,
    Employee emp2)
    {
        IComparable    icomp = (IComparable) emp1;
        return(icomp.CompareTo (emp2) <= 0);
    }
    public static bool operator >=(
    Employee emp1,
    Employee emp2)
    {
        IComparable    icomp = (IComparable) emp1;
        return(icomp.CompareTo (emp2) >= 0);
    }
    
    public override string ToString()
    {
        return(name + ":" + id);
    }
    
    string    name;
    int    id;
}

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