Decorator
The decorator design pattern allows you to add features to an object dynamically. An example would be the search functionality in an application. You may need to search for employees such as salary, zip code, skills, and so on. The user may choose to enter any combination of search criteria, and it would be a daunting task trying to figure out all the possible combination as the number of fields grow. The decorator pattern allows you to dynamically add only the fields that the user is searching for.