public CommandResult Execute()
 {
     _result = new CommandResult ("Exit");
     return _result;
 }
 public CommandResult Execute()
 {
     _result = new CommandResult ("List");
     _result.Data = _biblotica.GetBookList ();
     return _result;
 }
 public CommandResult Execute()
 {
     _result = new CommandResult ("Checkout");
     _result.Data = _biblotica.Checkout (_ISBNNumber);
     return _result;
 }
 public CommandResult Execute()
 {
     _result = new CommandResult("Provide a valid Input!!");
     return _result;
 }