Design Patterns

Design patterns are solutions to software design problems you find again and again in real-world application development. Patterns are about reusable designs and interactions of objects.

Design Patterns are in a continious phase of evolution, which means that they keep on getting better & better as they are tested against time, reliability and subjected to continious improvements. Further, design patterns have evolved towards targeting specific domains. For example, windows-based banking applications are usually based on singleton patterns, e-commerce web applications are based on the MVC (Model-View-Controller) pattern.

There are following 3 type of design patterns based on communication,structure,behavior of objects .

Creational Pattern:

It deals with object creation mechanisms.

Pattern	Description
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:

It eases the design by identifying a simple way to realize relationships between entities.

Pattern	Description
Adapter	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:

It describes how different objects and classes interact with each other to make things happen.

Pattern	Description
Chain of Responsibility	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
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

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Pankaj Maurya12y ago

Pattern	Description
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

Pattern	Description
Adapter	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

Pattern	Description
Chain of Responsibility	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
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

Jignesh Trivedi12y ago
a design pattern is a general reusable solution to a commonly occurring problem within a given context in software design.
it is not finished design that can be transformed directly into source or machine code. Patterns are formalized best practices that the programmer must implement in the application.
http://en.wikipedia.org/wiki/Software_architecture
There are many famous design patterns are available with c#
http://www.codeproject.com/Articles/28309/Design-pattern-FAQ-Part-1-Training
hope this will help you.
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