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贴子主题： C#快餐－4

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发信人: walts (休息一会), 信区: DotNET
标  题: C#快餐－4
发信站: BBS 水木清华站 (Thu Jul 26 01:20:54 2001)

Lesson 4 Object-Oriented design

  Object oriented programming is not a science but an art. Programming
is a hard, time consuming work with no perfect solutions. Widespread
use of personal computers have generated a demand for more and more
complex applications  which contain hundreds of thousands of lines of
code. This code needs to be updated, adjusted and debugged these tasks
often take as much time as would have been spent rewriting the application
from scratch. Productivity of a single programmer is very low compared
to a worker of another profession. While a milkman can milk dozens of cows
during his workday and a doctor can take care of dozens of patients.
An average programmer may write 100 or so lines of code which constitute .
1% of any useful application. So to simplify and expedite software development

  newer languages are developed to simplify and facilitate the tasks of the
software developer. Object oriented design is an attempt in this direction
.  In a few years something else will take its place, but today it is the
bestad hoc set of rules that each programmer strives to follow in her/his work.

    The idea of object oriented programming is very simple: Structure your
program in logical units. These units are  called objects but the name
sometimes sound more complicated than what it describes. The elements of

    object oriented design areInheritance:  Let a more specialized object
inherit from a more general object.

using System;
class Demo
{
   public class animal
   {
      int weight;
      string name;
      public void show()
      {
         Console.WriteLine ("{0} has weight {1}", name, weight);
      }
      public void my_set (int k, string z)
      {
         weight=k;
         name=z;
      }
   }
   public class tiger:animal
   {
      public tiger()
      {
         my_set(100,"tiger");
         show();
      }
   }
   public class lion:animal
   {
      public lion()
      {
         my_set(200,"lion");
         show();
      }
   }
    public static void Main()
   {
      tiger Mike = new tiger();
      lion Bob = new lion();
   }
}

   In the program above, classes  lion: and  tiger are derived from class
animal. Class animal  is called base class. Derivation is considered a good
idea if aderived class satisfies "is a " relationship with respect to the
base class.

  In our case tiger and lion are animals, so this relationship is satisfied.
Polymorphism: Use the same object to  perform  some logical task under
different circumstances
Encapsulation: Try giving  objects not more control to other objects than
necessary.

Try to give simple examples of Inheritance, Polymorphism and Encapsulation
in C#. Good Luck!

--

A great poem is a fountain forever overflowing with the
　waters of wisdom and delight.
　　　　　　　　　　　
                                          —— Shelley

※ 来源:·BBS 水木清华站 smth.org·[FROM: 166.111.142.118]
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