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

using System;

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

 using System;

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

 using System;

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

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

using System;

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

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

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");
    }
}

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();
    }
}

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();
    }
}

using System;

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

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();
        }
    }
}

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

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

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

#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();
    }
}

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();
    }
}

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);
        }
    }
}

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);
    }
}

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);
    }
}