using System;

​

public class Program

{

    public static void Main()

    {

        Action<string> messageTarget; 

        if (Environment.GetCommandLineArgs().Length > 1)

            messageTarget = ShowWindowsMessage;

        else

            messageTarget = Console.WriteLine;

​

        messageTarget("Hello, World!");  

    }

    private static void ShowWindowsMessage(string message)

    {

        //MessageBox.Show(message);      

    }

}

​