Design Patterns

                                                                                            Design Patterns

Design Patterns are about design and interaction of objects. They provide a communication platform concerning elegant, reusable solutions to commonly encountered programming challenges. It is a way to pursue an intent that uses classes and their methods in an OO language

Also we can say that, it is recurring solutions to software design problems you find again and again in real-world application development. Patterns are about design and interaction of objects, as well as providing a communication platform concerning elegant, reusable solutions to commonly encountered programming challenges.

With .NET the full capability of object-oriented programming came into the picture for the most of developers using Microsoft products.

You can do much more with .NET than with previous Microsoft technologies but it comes with a price, increased complexity. And design patterns have evolved over the time to help to keep things in order when applications become complex.

The Gang of Four (GoF) patterns are generally considered the foundation for all other patterns. They are categorized in three groups: Creational, Structural, and Behavioral.

Creational Patterns
Abstract Factory	Creates an instance of several families of classes
Builder	Separates object construction from its representation
Factory Method	Creates an instance of several derived classes
Prototype	A fully initialized instance to be copied or cloned
Singleton	A class of which only a single instance can exist

Structural Patterns
Adapter	Wrap an existing class with a new interface, Match interfaces of different classes
Bridge	Separates an object’s interface from its implementation
Composite	A tree structure of simple and composite objects
Decorator	Add responsibilities to objects dynamically
Facade	A single class that represents an entire subsystem
Flyweight	A fine-grained instance used for efficient sharing
Proxy	An object representing another object

Behavioral Patterns
Chain of Resp.	A way of passing a request between a chain of objects
Command	Encapsulate a command request as an object
Interpreter	A way to include language elements in a program
Iterator	Sequentially access the elements of a collection
Mediator	Defines simplified communication between classes
Memento	Capture and restore an object's internal state
Observer	A way of notifying change to a number of classes
State	Alter an object's behavior when its state changes
Strategy	Encapsulates an algorithm inside a class
Template Method	Defer the exact steps of an algorithm to a subclass
Visitor	Defines a new operation to a class without change

We can also categorize it :-

Interface Patterns

1     Adapter

2     Facade

3     Composite

4     Bridge

 Responsibility Patterns

1     Singleton

2     Observer

3     Mediator

4     Proxy

5     Chain of Responsibility

6     Flyweight

Construction Patterns

1     Builder

2     Factory Method

3     Abstract Factory

4     Prototype

5     Memento

Operation Patterns

1      Template Method

2     State

3     Strategy

4     Command

5     Interpreter

Extension Patterns

1     Decorator

2     Iterator

3     Visitor