Command_Exercise.cs

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using System;
using System.Collections.Generic;
using System.Text;
 
namespace DesignPatternExamples_csharp
{
    internal class Command_Exercise
    {
 
        Stack<Command> _commandUndoList = new Stack<Command>();
 
        void Command_Save_And_Execute(Command_TextObject text, Command command)
        {
            _commandUndoList.Push(command);
            command.Execute();
        }
 
        void Command_Operation_Replace(Command_TextObject source, string searchPattern, string replaceText)
        {
            source.Text = source.Text.Replace(searchPattern, replaceText);
        }
 
        void Command_Operation_Reverse(Command_TextObject source)
        {
            StringBuilder output = new StringBuilder();
            string text = source.Text;
            for (int index = 0; index < text.Length; ++index)
            {
                output.Append(text[text.Length - 1 - index]);
            }
            source.Text = output.ToString();
        }
 
        void Command_Undo(Command_TextObject text)
        {
            if (_commandUndoList.Count > 0)
            {
                // Reset the text to the starting point.
                text.Reset();
 
                // Get rid of the last command applied and remember it.
                Command lastCommand = _commandUndoList.Pop();
 
                // Now apply all remaining commands to the text in order.
                foreach (Command command in _commandUndoList)
                {
                    command.Execute();
                }
 
                // Show off what we (un)did.
                Console.WriteLine("    undoing command {0,-31}: \"{1}\"", lastCommand, text);
            }
        }
 
        void Command_ApplyReplaceCommand(Command_TextObject text, string searchPattern, string replaceText)
        {
            Command command = new Command(text, "Replace", Command_Operation_Replace, searchPattern, replaceText);
            Command_Save_And_Execute(text, command);
            Console.WriteLine("    command {0,-31}: \"{1}\"", command, text);
        }
 
 
        void Command_ApplyReverseCommand(Command_TextObject text)
        {
            Command command = new Command(text, "Reverse", Command_Operation_Reverse);
            Command_Save_And_Execute(text, command);
            Console.WriteLine("    command {0,-31}: \"{1}\"", command, text);
        }
 
 
        // ! [Using Command in C#]
        public void Run()
        {
            Console.WriteLine();
            Console.WriteLine("Command Exercise");
 
            // Start with a fresh undo list.
            _commandUndoList.Clear();
 
            // The base text object to work from.
            Command_TextObject text = new Command_TextObject("This is a line of text on which to experiment.");
 
            Console.WriteLine("  Starting text: \"{0}\"", text);
 
            // Apply four operations to the text.
            Command_ApplyReplaceCommand(text, "text", "painting");
            Command_ApplyReplaceCommand(text, "on", "off");
            Command_ApplyReverseCommand(text);
            Command_ApplyReplaceCommand(text, "i", "!");
 
            Console.WriteLine("  Now perform undo until back to original");
 
            // Now undo the four operations.
            Command_Undo(text);
            Command_Undo(text);
            Command_Undo(text);
            Command_Undo(text);
 
            Console.WriteLine("  Final text   : \"{0}\"", text);
 
            Console.WriteLine("  Done.");
        }
        // ! [Using Command in C#]
    }
}