Strategy Design Pattern

 definition
 UML diagram
 participants
 sample code in C#



definition

Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.

Frequency of use:   medium high

UML class diagram


participants

    The classes and/or objects participating in this pattern are:

  • Strategy  (SortStrategy)
    • declares an interface common to all supported algorithms. Context uses this interface to call the algorithm defined by a ConcreteStrategy
  • ConcreteStrategy  (QuickSort, ShellSort, MergeSort)
    • implements the algorithm using the Strategy interface
  • Context  (SortedList)
    • is configured with a ConcreteStrategy object
    • maintains a reference to a Strategy object
    • may define an interface that lets Strategy access its data.

sample code in C#

This structural code demonstrates the Strategy pattern which encapsulates functionality in the form of an object. This allows clients to dynamically change algorithmic strategies.

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// Strategy pattern -- Structural example




This real-world code demonstrates the Strategy pattern which encapsulates sorting algorithms in the form of sorting objects. This allows clients to dynamically change sorting strategies including Quicksort, Shellsort, and Mergesort.

Show code

// Strategy pattern -- Real World example




This .NET optimized code demonstrates the same real-world situation as above but uses modern, built-in .NET features, such as, generics, reflection, object initializers, automatic properties, etc.

Show code

// Strategy pattern -- .NET optimized




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.NET
Design Pattern
Framework 4.5


 
C# and VB.NET


   Includes:

  Gang of Four Patterns
  Head First Patterns
  Enterprise Patterns
  Multi-Tier Patterns

  Repository Pattern
  Unit-of-Work Pattern
  CQRS Pattern
  Active Record Pattern

  Model View Controller
  Model View Presenter
  Model View ViewModel

  SparkTM RAD Platform
  Art Shop MVC Application
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