Month: February 2011

Properties Accessors

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

Publisher: Apress  L.P.
ISBN: 1-893115-62-3
*/
// 18 - PropertiesAccessors
// copyright 2000 Eric Gunnerson

public class PropertiesAccessors
{
    private string name;
    
    public string Name
    {
        get 
        {
            return name;
        }
        set 
        {
            name = value;
        }
    }
}

Properties: Side Effects When Setting Values

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

Publisher: Apress  L.P.
ISBN: 1-893115-62-3
*/
// 18 - PropertiesSide Effects When Setting Values
// copyright 2000 Eric Gunnerson
using System;
using System.Collections;
class Basket
{
    internal void UpdateTotal()
    {
        total = 0;
        foreach (BasketItem item in items)
        {
            total += item.Total;
        }
    }
    
    ArrayList    items = new ArrayList();
    Decimal    total;
}
public class BasketItem
{
    BasketItem(Basket basket)
    {
        this.basket = basket;
    }
    public int Quantity
    {
        get
        {
            return(quantity);
        }
        set
        {
            quantity = value;
            basket.UpdateTotal();
        }
    }
    public Decimal Price
    {
        get
        {
            return(price);
        }
        set
        {
            price = value;
            basket.UpdateTotal();
        }
    }
    public Decimal Total
    {
        get
        {
            // volume discount; 10% if 10 or more are purchased
            if (quantity >= 10)
            return(quantity * price * 0.90m);
            else
            return(quantity * price); 
        }
    }
    
    int        quantity;     // count of the item
    Decimal    price;        // price of the item
    Basket     basket;       // reference back to the basket
}

Properties: Use of Properties

Posted on by coder
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/*
A Programmer's Introduction to C# (Second Edition)
by Eric Gunnerson

Publisher: Apress  L.P.
ISBN: 1-893115-62-3
*/
// 18 - PropertiesUse of Properties
// copyright 2000 Eric Gunnerson
using System;
public class Auto
{
    public Auto(int id, string name)
    {
        this.id = id;
        this.name = name;
    }
    
    // query to find # produced
    public int ProductionCount
    {
        get
        {
            if (productionCount == -1)
            {
                // fetch count from database here.
            }
            return(productionCount);
        }
    }
    public int SalesCount
    {
        get
        {
            if (salesCount == -1)
            {
                // query each dealership for data
            }
            return(salesCount);
        }
    }
    string name;
    int id;
    int productionCount = -1;
    int salesCount = -1;
}

access to a private field through a property

Posted on by coder
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/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa

Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
//
// Property.cs — Demonstrates access to a private field through a property.
// Compile this program with the following command line:
// C:>csc Property.cs
//
namespace nsProperty
{
using System;
public class Property
{
const double radian = 57.29578;
const double pi = 3.14159;
int Angle
{
get
{
int angle = (int) (fAngle * radian + 0.5);
angle = angle == 360 ? 0 : angle;
return (angle);
}
set
{
double angle = (double) value / radian;
if (angle < (2 * pi)) { fAngle = angle; Console.WriteLine ("fAngle set to {0,0:F5}", fAngle); } else { Console.WriteLine ("fAngle not modified"); } } } double fAngle = 0.0; // Angle in radians static public int Main (string [] args) { int angle; try { angle = int.Parse (args[0]); } catch (IndexOutOfRangeException) { Console.WriteLine ("usage: circle [angle in degrees]"); return (-1); } catch (FormatException) { Console.WriteLine ("Please use a number value for the angle in degrees"); return (-1); } Property main = new Property(); main.Angle = angle; Console.WriteLine ("The angle is {0} degrees", main.Angle); return (0); } } } [/csharp]

The use of an abstract property

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/*
C# Programming Tips &amp; Techniques
by Charles Wright, Kris Jamsa

Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/

//
// Abstract.cs -- Demonsrates the use of an abstract property.
//
//                Compile this program with the following command line:
//                    C:>csc Abstract.cs
//
namespace nsAbstract
{
    using System;
    using System.Runtime.InteropServices;
    public class AbstractPro
    {
        static public void Main ()
        {
            Console.WriteLine (clsAbstract.StaticMethod());
        }
    }
    //
    // To use the abstract modifier on a method, the class also must
    // be declared as abastract
    abstract class clsAbstract
    {
    //
    // To declare an abstract method, end the declaration with a semicolon.
    // Do not provide a body for the method.
        abstract public int AbstractMethod();
    //
    // An abstract class may contain a static method. You do not have
    // to declare an instance of the class to access a static method
        static public double StaticMethod()
        {
            return (3.14159 * 3.14159);
        }
        abstract public long Prop
        {
            get;
            set;
        }
    }
    //
    // Inherit from the abstract class. The following class implements
    // the AbstractMethod().
    // The access level of the derived class method must be the same
    // as the access level of the base class abstract method.
    class clsDerivedFromAbstract : clsAbstract
    {
        override public int AbstractMethod()
        {
            return (0);
        }
        override public long Prop
        {
            get
            {
                return (val);
            }
            set
            {
                val = value;
            }
        }
        private long val;
    }
}

Illustrates the use of a property

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

Publisher: Sybex;
ISBN: 0782129110
*/
/*
  Example6_4.cs illustrates the use of a property
*/


// declare the Car class
class Car
{

  // declare a private field
  private string make;

  // declare a property
  public string Make
  {
    get
    {
      return make;
    }
    set
    {
      make = value;
    }
  }

}


public class Example6_4
{

  public static void Main()
  {

    // create a Car object
    System.Console.WriteLine("Creating a Car object");
    Car myCar = new Car();

    // set the Car Make
    System.Console.WriteLine("Setting the Car object&#039;s Make property to Porsche");
    myCar.Make = "Porsche";

    System.Console.WriteLine("myCar.Make = " + myCar.Make);

  }

}

Demonstrates the use of properties to control how values are saved in fields

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/*
C# Programming Tips &amp; Techniques
by Charles Wright, Kris Jamsa

Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/

//  Rect.cs - Demonstrates the use of properties to control how values are
//            saved in fields
//
//            This is a Visual Studio project. To compile outside of Visual
//            Studio, use the following command line:
//                C:>csc rect.cs
//
using System;
using System.Drawing;

namespace nsRect
{
  struct POINT
  {
    public POINT (int x, int y)
    {
      this.cx = x;
      this.cy = y;
    }
    public int cx;
    public int cy;
    public override string ToString ()
    {
      return (String.Format ("({0}, {1})", cx, cy));
    }
  }
  struct RECT
  {
    public RECT (Rectangle rc)
    {
      m_UpperLeft.cx = rc.X;
      m_UpperLeft.cy = rc.Y;
      m_LowerRight.cx = rc.X + rc.Width;
      m_LowerRight.cy = rc.Y + rc.Height;
    }
    // Define constructors
    public RECT (POINT pt1, POINT pt2)
    {
      m_UpperLeft = pt1;
      m_LowerRight = pt2;
    }
    public RECT (int x1, int y1, int x2, int y2)
    {
      m_UpperLeft.cx = x1;
      m_UpperLeft.cy = y1;
      m_LowerRight.cx = x2;
      m_LowerRight.cy = y2;
    }
    public RECT (POINT pt1, int Width, int Height)
    {
      m_UpperLeft.cx = pt1.cx;
      m_UpperLeft.cy = pt1.cy;
      m_LowerRight.cx = pt1.cx + Width;
      m_LowerRight.cy = pt1.cy + Height;
    }
    // Property to get and set the upper left point
    public POINT UpperLeft
    {
      get {return (m_UpperLeft);}
      set {m_UpperLeft = value;}
    }
    // Property to get and set the lower right point
    public POINT LowerRight
    {
      get {return (m_LowerRight);}
      set {m_LowerRight = value;}
    }
    // Property to return a normalized System.Drawing.ectangle object
    public System.Drawing.Rectangle Rectangle
    {
      get
      {
        RECT rc = Normal;
        return (new Rectangle (rc.UpperLeft.cx, rc.UpperLeft.cy,
          rc.LowerRight.cx - rc.UpperLeft.cx,
          rc.LowerRight.cy - rc.UpperLeft.cy));
      }
    }
    // Property to return a normalized copy of this rectangle
    public RECT Normal
    {
      get
      {
        return (new RECT (
          Math.Min (m_LowerRight.cx, m_UpperLeft.cx),
          Math.Min (m_LowerRight.cy, m_UpperLeft.cy),
          Math.Max (m_LowerRight.cx, m_UpperLeft.cx),
          Math.Max (m_LowerRight.cy, m_UpperLeft.cy))
          );

      }
    }
    private POINT m_UpperLeft;
    private POINT m_LowerRight;
    public override string ToString()
    {
      return (String.Format ("Upper left = {0}; Lower right = {1}",
        m_UpperLeft, m_LowerRight));
    }
  }
  public class Rect
  {
    static public void Main ()
    {
      // Define a "normal" rectangle
      POINT pt1 = new POINT (-10,30);
      POINT pt2 = new POINT (100, 100);
      RECT rc = new RECT (pt1, pt2);
      Console.WriteLine ("RECT: " + rc);
      Console.WriteLine ("Normal: " + rc.Normal);
      Console.WriteLine ("Rectangle: " + rc.Rectangle + "
");
      // Define a rectangle with normal x but not y
      pt1.cx = 100;
      pt1.cy = 50;
      pt2.cx = 200;
      pt2.cy = 20;
      rc.UpperLeft = pt1;
      rc.LowerRight = pt2;
      Console.WriteLine ("RECT: " + rc);
      Console.WriteLine ("Normal: " + rc.Normal);
      Console.WriteLine ("Rectangle: " + rc.Rectangle + "
");
      // Define a rectangle with normal y but not x
      pt1.cx = 200;
      pt1.cy = 50;
      pt2.cx = 100;
      pt2.cy = 80;
      rc.UpperLeft = pt1;
      rc.LowerRight = pt2;
      Console.WriteLine ("RECT: " + rc);
      Console.WriteLine ("Normal: " + rc.Normal);
      Console.WriteLine ("Rectangle: " + rc.Rectangle + "
");
      // Define a rectangle with both values of upper left greater than the lower y
      pt1.cx = 225;
      pt1.cy = 180;
      pt2.cx = 25;
      pt2.cy = 35;
      rc.UpperLeft = pt1;
      rc.LowerRight = pt2;
      Console.WriteLine ("RECT: " + rc);
      Console.WriteLine ("Normal: " + rc.Normal);
      Console.WriteLine ("Rectangle: " + rc.Rectangle + "
");
      // Define a rectangle with points equal
      pt1.cx = 75;
      pt1.cy = 150;
      pt2.cx = 75;
      pt2.cy = 150;
      rc.UpperLeft = pt1;
      rc.LowerRight = pt2;
      Console.WriteLine ("RECT: " + rc);
      Console.WriteLine ("Normal: " + rc.Normal);
      Console.WriteLine ("Rectangle: " + rc.Rectangle + "
");
    }
  }
}