C# Design Patterns

What are Design Patterns?

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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.

The 23 Gang of Four (GoF) patterns are generally considered the foundation for all
other patterns. They are categorized in three groups: Creational, Structural, and
Behavioral (for a complete list see below). This reference provides source code for
each of the 23 GoF patterns.

C# Design Patterns

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To give you a head start, the C# source code for each pattern is provided
in 2 forms: structural and real-world. Structural code
uses type names as defined in the pattern definition and UML diagrams.
Real-world code provides real-world programming situations where you may use
these patterns.

A third form, .NET optimized, demonstrates
design patterns that fully exploit built-in .NET features, such as, generics,
delegates, reflection, and more. These and much more are available in
our Dofactory .NET product.
See the Singleton page
for a .NET Optimized example.

Creational Patterns

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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

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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

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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

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