Gang of Four (GOF) Design Patterns in .Net

 In 1994, four authors Erich Gamma, Richard Helm, Ralph Johnson and John Vlissides published a book (Design Patterns: Elements of Reusable Object-Oriented Software) for explaining the concept of Design Pattern in Software development. These four authors are collectively known as Gang of Four (GOF).

GOF Design Patterns

The 23 Design patterns are defined by the Gang of Four programmers. These 23 patterns are divided into three groups depending on the nature of the design problem they intend to solve.

1. Creational Design Patterns

   These patterns deal with the process of objects creation in such a way that they can be decoupled from their implementing system. This provides more flexibility in deciding which objects need to be created for a given use case/ scenario. There are as follows:
   1. Factory Method : Create instances of derived classes
   2. Abstract Factory : Create instances of several classes belonging to different families
   3. Builder : Separates an object construction from its representation
   4. Prototype : Create a duplicate object or clone of the object
   5. Singleton : Ensures that a class can has only one instance

2. Structural Design Patterns

   These patterns deal with the composition of objects structures. The concept of inheritance is used to compose interfaces and define various ways to compose objects for obtaining new functionalities. There are as follows:
   1. Adapter : Match interfaces of different classes
   2. Bridge : Separates an object’s abstraction from its implementation
   3. Composite : A tree structure of simple and composite objects
   4. Decorator : Add responsibilities to objects dynamically
   5. Façade : A single class that represents an entire complex system
   6. Flyweight : Minimize memory usage by sharing as much data as possible with similar objects
   7. Proxy : Provides a surrogate object, which references to other object

3. Behavioral Design Patterns

   These patterns deal with the process of communication, managing relationships, and responsibilities between objects. There are as follows:
   1. Chain of Responsibility: Passes a request among a list or chain of objects.
   2. Command: Wraps a request under an object as a command and passed to invoker object.
   3. Interpreter
   4. Iterator
   5. Mediator
   6. Memento
   7. Observer
   8. State
   9. Strategy
   10. Visitor
   11. Template Method