17种Hello World！

使用C#编写不同的“Hello World”程序

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);

}

} 

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