static void TestUndoableCommand() { var history = new Command.Editor.History(); var document = new Command.Editor.HtmlDocument(); document.Content = "Hello World"; var boldCommand = new BoldCommand(document, history); boldCommand.Execute(); System.Console.WriteLine(document.Content); document.Content = "This is Command Pattern"; boldCommand = new BoldCommand(document, history); boldCommand.Execute(); System.Console.WriteLine(document.Content); var undoCommand = new UndoCommand(history); undoCommand.Execute(); System.Console.WriteLine(document.Content); undoCommand.Execute(); System.Console.WriteLine(document.Content); }