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Composite Pattern Motivation There are times when a program needs to manipulate a tree data structure and it is necessary to treat both Branches as well as Leaf Nodes uniformly. Consider for example a program that manipulates a file system. A file system is a tree structure that contains Branches which are Folders as well as Leaf nodes which are Files. Note that a folder object usually contains ..

Iterator Motivation One of the most common data structures in software development is what is generic called a collection. A collection is just a grouping of some objects. They can have the same type or they can be all cast to a base type like object. A collection can be a list, an array, a tree and the examples can continue. But what is more important is that a collection should provide a way t..

Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used.On the same idea is the template method is based. A template method defines an algorithm in a base class using abstract operations that sub..

ClickOnce is a Microsoft technology that enables the user to install and run a Windows application by clicking a link in a web page. (Such applications are known as Smart clients.) ClickOnce is a component of Microsoft .NET Framework 2.0 and later, supports deploying applications made with Windows Forms or Windows Presentation Foundation. It is similar to Java Web Start for the Java Platform or ..

Intent Provide a unified interface to a set of interfaces in a subsystem. Facade defines a higher-level interface that makes the subsystem easier to use.Wrap a complicated subsystem with a simpler interface.Problem A segment of the client community needs a simplified interface to the overall functionality of a complex subsystem. Discussion Facade discusses encapsulating a complex subsystem withi..

Motivation The adapter pattern is adapting between classes and objects. Like any adapter in the real world it is used to be an interface, a bridge between two objects. In real world we have adapters for power supplies, adapters for camera memory cards, and so on. Probably everyone have seen some adapters for memory cards. If you can not plug in the camera memory in your laptop you can use and ad..

“An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from the reunion of a set of other commands, in a given order. Just as a macro, the C..

Motivation Sometimes it's important to have only one instance for a class. For example, in a system there should be only one window manager (or only a file system or only a print spooler). Usually singletons are used for centralized management of internal or external resources and they provide a global point of access to themselves. The singleton pattern is one of the simplest design patterns: i..

Motivation Also known as Virtual Constructor, the Factory Method is related to the idea on which libraries work: a library uses abstract classes for defining and maintaining relations between objects. One type of responsibility is creating such objects. The library knows when an object needs to be created, but not what kind of object it should create, this being specific to the application using..

Motivation Modularization is a big issue in today's programming. Programmers all over the world are trying to avoid the idea of adding code to existing classes in order to make them support encapsulating more general information. Take the case of a information manager which manages phone number. Phone numbers have a particular rule on which they get generated depending on areas and countries. If..