Software Design Patterns

Software Design Patterns: Examples in C# for Creational, Structural, Behavioural design patterns.

Creational design patterns

1. Abstract Factory

   Creates an instance of several families of classes
   

2. Builder

   Separates object construction from its representation
   

3. Factory Method

   Creates an instance of several derived classes
   

4. Object Pool

   Avoid expensive acquisition and release of resources by recycling objects that are no longer in use
   

5. Prototype

   A fully initialized instance to be copied or cloned
   

6. Singleton

• A class of which only a single instance can exist

• This pattern is used when we want to ensure that only one object of a specific class needs to be created. All future references to the objects are referred to the same underlying instance created.

• Singleton controls concurrent access to the same resource.

• It ensures that, there is only one object available across the application in a controller state.

• Make sure to provide global access to the instance by

  • Making sure all constructors of the class is declared as private
  • Provide static method that returns a reference to the instance.
  • The instance is tored as a private static variable.
  • Make sure to delcare class as sealed.

Structural design patterns

1. Adapter

       Match interfaces of different classes
   

2. Bridge

Separates an object’s interface from its implementation

3. Composite

A tree structure of simple and composite objects

4. Decorator

Add responsibilities to objects dynamically

5. Facade

A single class that represents an entire subsystem

6. Flyweight

A fine-grained instance used for efficient sharing

7. Private Class Data

Restricts accessor/mutator access

8. Proxy

An object representing another object

Behavioral design patterns

1. Chain of responsibility

A way of passing a request between a chain of objects

2. Command

Encapsulate a command request as an object

3. Interpreter

A way to include language elements in a program

4. Iterator

Sequentially access the elements of a collection

5. Mediator

Defines simplified communication between classes

6. Memento

Capture and restore an object's internal state

7. Null Object

Designed to act as a default value of an object

8. Observer

A way of notifying change to a number of classes

9. State

Alter an object's behavior when its state changes

10. Strategy

Encapsulates an algorithm inside a class

11. Template method

Defer the exact steps of an algorithm to a subclass

12. Visitor

Defines a new operation to a class without change