static void CommandPattern()
{
Console.WriteLine("\n\nCommandPattern Pattern");
var history = new History();
var exampleService = new ExampleService("Initial value");
var exampleCommand = new ExampleCommand(history, exampleService);
var undoCommand = new UndoCommand <string>(history);
Console.WriteLine(exampleService.GetContent());
exampleCommand.Execute();
Console.WriteLine(exampleService.GetContent());
undoCommand.Execute();
Console.WriteLine(exampleService.GetContent());
}