Memento_Exercise.cs

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using System;
using System.Collections.Generic;
using System.Text;
 
namespace DesignPatternExamples_csharp
{
    internal class Memento_Exercise
    {
 
        Stack<IMemento> _mementoUndoList = new Stack<IMemento>();
 
        void Memento_SaveForUndo(Memento_TextObject text, string operation)
        {
            IMemento memento = text.GetMemento(operation);
            _mementoUndoList.Push(memento);
        }
 
 
        void Memento_Operation_Replace(Memento_TextObject source, string searchPattern, string replaceText)
        {
            source.Text = source.Text.Replace(searchPattern, replaceText);
        }
 
        void Memento_Operation_Reverse(Memento_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 Memento_Undo(Memento_TextObject text)
        {
            if (_mementoUndoList.Count > 0)
            {
                IMemento lastMemento = _mementoUndoList.Pop();
                text.RestoreMemento(lastMemento);
 
                // Show off what we (un)did.
                Console.WriteLine("    undoing operation {0,-31}: \"{1}\"", lastMemento.Name, text);
            }
        }
 
        void Memento_ApplyReplaceOperation(Memento_TextObject text, string searchPattern, string replaceText)
        {
            string operationName = String.Format("Replace '{0}' with '{1}'", searchPattern, replaceText);
            Memento_SaveForUndo(text, operationName);
            Memento_Operation_Replace(text, searchPattern, replaceText);
            Console.WriteLine("    operation {0,-31}: \"{1}\"", operationName, text);
        }
 
 
        void Memento_ApplyReverseOperation(Memento_TextObject text)
        {
            string operationName = "Reverse";
            Memento_SaveForUndo(text, operationName);
            Memento_Operation_Reverse(text);
            Console.WriteLine("    operation {0,-31}: \"{1}\"", operationName, text);
        }
 
        // ! [Using Memento in C#]
        public void Run()
        {
            Console.WriteLine();
            Console.WriteLine("Memento Exercise");
 
            // Start with a fresh undo list.
            _mementoUndoList.Clear();
 
            // The base text object to work from.
            Memento_TextObject text = new Memento_TextObject("This is a line of text on which to experiment.");
 
            Console.WriteLine("  Starting text: \"{0}\"", text);
 
            // Apply four operations to the text.
            Memento_ApplyReplaceOperation(text, "text", "painting");
            Memento_ApplyReplaceOperation(text, "on", "off");
            Memento_ApplyReverseOperation(text);
            Memento_ApplyReplaceOperation(text, "i", "!");
 
            Console.WriteLine("  Now perform undo until back to original");
 
            // Now undo the four operations.
            Memento_Undo(text);
            Memento_Undo(text);
            Memento_Undo(text);
            Memento_Undo(text);
 
            Console.WriteLine("  Final text   : \"{0}\"", text);
 
            Console.WriteLine("  Done.");
        }
        // ! [Using Memento in C#]
    }
}