Null_Object.cs

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using System;
using System.Collections.Generic;
 
namespace DesignPatternExamples_csharp
{
    public abstract class MoveCommand
    {
        public string Name { get; private set; }
 
        public string Command { get; private set; }
 
 
        public MoveCommand(string command, string commandName)
        {
            Command = command;
            Name = commandName;
        }
 
 
        public void Show()
        {
            Console.WriteLine("    '{0}' -> {1}", Command, Name);
        }
 
 
        public abstract void Execute();
    }
 
 
    //########################################################################
    //########################################################################
 
 
    class MoveCommandLeft : MoveCommand
    {
        public MoveCommandLeft(string command) : base(command, "Left")
        {
        }
 
 
        public override void Execute()
        {
            Console.Write("move left");
        }
    }
 
 
    //########################################################################
    //########################################################################
 
 
    class MoveCommandRight : MoveCommand
    {
        public MoveCommandRight(string command) : base(command, "Right")
        {
        }
 
 
        public override void Execute()
        {
            Console.Write("move right");
        }
    }
 
 
    //########################################################################
    //########################################################################
 
 
    class MoveCommandUp : MoveCommand
    {
        public MoveCommandUp(string command) : base(command, "Up")
        {
        }
 
 
        public override void Execute()
        {
            Console.Write("move up");
        }
    }
 
 
    //########################################################################
    //########################################################################
 
 
    class MoveCommandDown : MoveCommand
    {
        public MoveCommandDown(string command) : base(command, "Down")
        {
        }
 
 
        public override void Execute()
        {
            Console.Write("move down");
        }
    }
 
 
    //########################################################################
    //########################################################################
 
 
    class MoveCommandNone : MoveCommand
    {
        public MoveCommandNone(string command) : base(command, "None")
        {
        }
 
 
        public override void Execute()
        {
        }
    }
 
 
    //########################################################################
    //########################################################################
 
 
    public class MoveProcessor
    {
        //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
        // Private methods.
 
        private List<MoveCommand> _ParseMoves(string moveList)
        {
            List<MoveCommand> commands = new List<MoveCommand>();
            foreach (char command in moveList)
            {
                string testCommand = command.ToString().ToUpper();
                MoveCommand moveCommand;
 
                switch (testCommand)
                {
                    case "U":
                        moveCommand = new MoveCommandUp(command.ToString());
                        break;
 
                    case "D":
                        moveCommand = new MoveCommandDown(command.ToString());
                        break;
 
                    case "L":
                        moveCommand = new MoveCommandLeft(command.ToString());
                        break;
 
                    case "R":
                        moveCommand = new MoveCommandRight(command.ToString());
                        break;
 
                    default:
                        // Everything else is a "do nothing" command.
                        moveCommand = new MoveCommandNone(command.ToString());
                        break;
                }
                commands.Add(moveCommand);
            }
 
            return commands;
        }
 
 
        private void _ExecuteMoves(List<MoveCommand> commands)
        {
            foreach(MoveCommand command in commands)
            {
                Console.Write("<");
                command.Execute();
                Console.Write("> ");
            }
            Console.WriteLine();
        }
 
 
        private void _ShowMoves(List<MoveCommand> commands)
        {
            foreach(MoveCommand command in commands)
            {
                command.Show();
            }
        }
 
        //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
        // Public methods.
 
        public void ExecuteMoveList(string moveList)
        {
            List<MoveCommand> commands = _ParseMoves(moveList);
            _ExecuteMoves(commands);
        }
 
 
        public void ShowMoveList(string moveList)
        {
            List<MoveCommand> commands = _ParseMoves(moveList);
            _ShowMoves(commands);
        }
    }
}