面向对象的问题：过度封装

1. A Beginners Hello World

public class HelloWorld
{
   public static void Main()
   {
     System.Console.WriteLine("HELLO WORLD");
   }
}

2. Slightly improved version

using System;
public class HelloWorld
{
   public static void Main()
   {
     Console.WriteLine("HELLO WORLD");
   }
}

3. Command Line Arguments

using System;
public class HelloWorld
{
   public static void Main(string[] args)
   {
     Console.WriteLine(args[0]);
   }
}

4. From Constructor

using System;
public class HelloWorld
{
   public HelloWorld()
   {
     Console.WriteLine("HELLO WORLD");
   }

   public static void Main()
   {
     HelloWorld hw = new HelloWorld();
   }
}

5. More OO

using System;
public class HelloWorld
{
   public void helloWorld()
   {
     Console.WriteLine("HELLO WORLD");
   }

   public static void Main()
   {
     HelloWorld hw = new HelloWorld();
     hw.HelloWorld();
   }
}

6. From another class

using System;
public class HelloWorld
{
   public static void Main()
   {
     HelloWorldHelperClass hwh = new HelloWorldHelperClass();
     hwh.writeHelloWorld();
   }
}

public class HelloWorldHelperClass
{
   public void writeHelloWorld()
   {
     Console.WriteLine("Hello World");
   }
}

7. Inheritance

abstract class HelloWorldBase
{
   public abstract void writeHelloWorld();
}
class HelloWorld : HelloWorldBase
{
   public override void writeHelloWorld()
   {
     Console.WriteLine("Hello World");
   }
}
class HelloWorldImp
{
   static void Main() {
     HelloWorldBase hwb = HelloWorld;
     HelloWorldBase.writeHelloWorld();
   }
}

8. Static Constructor

using System;
public class HelloWorld
{
   private static string strHelloWorld;

   static HelloWorld()
   {
     strHelloWorld = "Hello World";
   }
   void writeHelloWorld()
   {
     Console.WriteLine(strHelloWorld);
   }

   public static void Main()
   {
     HelloWorld hw = new HelloWorld();
     hw.writeHelloWorld();
   }
}

9. Exception Handling

using System;
public class HelloWorld
{
   public static void Main(string[] args)
   {
     try
     {
       Console.WriteLine(args[0]);
     }
     catch(IndexOutOfRangeException e)
     {
       Console.WriteLine(e.ToString());
     }
   }
}

10. Creating a DLL and using it in an application

using System;
namespace HelloLibrary
{
   public class HelloMessage
   {
     public string Message
     {
       get
       {
         return "Hello, World!!!";
       }
     }
   }
}

//------

using System;
using HelloLibrary;

namespace HelloApplication
{
   class HelloApp
   {

     public static void Main(string[] args)
     {
       HelloMessage m = new HelloMessage();

     }
   }
}

11. Using Property

using System;
public class HelloWorld
{
   public string strHelloWorld
   {
     get
     {
       return "Hello World";
     }
   }

   public static void Main()
   {
     HelloWorld hw = new HelloWorld();
     Console.WriteLine(cs.strHelloWorld);
   }
}

12. Using Delegates

using System;
class HelloWorld
{
   static void writeHelloWorld() {
     Console.WriteLine("HelloWorld");
   }
   static void Main() {
     SimpleDelegate d = new SimpleDelegate(writeHelloWorld);
     d();
   }
}

13. Using Attributes

#define DEBUGGING
using System;
using System.Diagnostics;

public class HelloWorld : Attribute
{
   [Conditional("DEBUGGING")]

   public void writeHelloWorld()
   {
     Console.WriteLine("Hello World");
   }

   public static void Main()
   {
     HelloWorld hw = new HelloWorld();

     hw.writeHelloWorld();
   }
}

14. Using Interfaces

using System;
interface IHelloWorld
{
   void writeHelloWorld();
}

public class HelloWorld : IHelloWorld
{
   public void writeHelloWorld()
   {
     Console.WriteLine("Hello World");
   }

   public static void Main()
   {
     HelloWorld hw = new HelloWorld();

     hw.writeHelloWorld();
   }
}

15. Dynamic Hello World

using System;
using System.Reflection;

namespace HelloWorldNS
{

   public class HelloWorld
   {
     public string writeHelloWorld()
     {
       return "HelloWorld";
     }

     public static void Main(string[] args)
     {
       Type hw = Type.GetType(args[0]);

       // Instantiating a class dynamically

       object[] nctorParams = new object[] {};
       object nobj = Activator.CreateInstance(hw,
               nctorParams);

       // Invoking a method

       object[] nmthdParams = new object[] {};
       string strHelloWorld = (string) hw.InvokeMember(
               "writeHelloWorld", BindingFlags.Default |
               BindingFlags.InvokeMethod, null,
               nobj, nmthdParams);

       Console.WriteLine(strHelloWorld);
     }
   }
}

16. Unsafe Hello World

using System;
public class HelloWorld
{
   unsafe public void writeHelloWorld(char[] chrArray)
   {
     fixed(char *parr = chrArray)
     {
       char *pch = parr;
       for(int i=0; i<chrArray.Length; i++)
         Console.Write(*(pch+i));
     }
   }

   public static void Main()
   {
     HelloWorld hw = new HelloWorld();
     char[] chrHelloWorld = new char[]
         {‘H‘,‘e‘,‘l‘,‘l‘,‘o‘, ‘ ‘, ‘W‘,‘o‘,‘r‘,‘l‘,‘d‘};
     hw.writeHelloWorld(chrHelloWorld);
   }
}

17. Using InteropServices

using System;
using System.Runtime.InteropServices;

class Class1
{
   [DllImport("kernel32")]
   private static extern int Beep(int dwFreq, int dwDuration);

   static void Main(string[] args)
   {
     Console.WriteLine("Hello World");
     Beep(1000, 2000);