不一样的入门：看C# Hello World的17种写法

摘要：本文针对不同阶段、不同程度的C#学习者，介绍了C# Hello World的17种不同写法，希望会对大家有所帮助。(C# Hello World写法入门、C# Hello World写法进阶、C# Hello World的特别写法三种角度进行推进)，本人觉得非常有趣，有兴趣的可以好好学习下。

C# Hello World写法入门:

1. 初学者

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

2. 改进的HELLO WORLD

using System;

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

 3. 命令行形式

using System;

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

 4. 构造函数

using System;

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

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

C# Hello World写法进阶:

5. 面向对象

using System;

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

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

6. 从其他类

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. 继承

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. 静态构造函数

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. 异常处理

using System;

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

10. 名字空间

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. 属性

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. 代理

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

13. 使用属性

#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. 接口

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();
    }
}

C# Hello World的特别写法:

15. 动态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);//, 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. 不安全代码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. 使用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);
    }
}