Singleton Design Pattern -- Design Pattern

Ensure a class has only one instance and provide a global point of access to it

Participants:

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

• Singleton(Load Balancer)

          Defines an Instance operation that lets clients access its unique instance. Instance is a class operation. Responsible for creating and maintaining its own unique instance.

Sample Code:

using System;  namespace Singleton.Structural {   /// <summary>   /// MainApp startup class for Structural   /// Singleton Design Pattern.   /// </summary>   class MainApp   {     /// <summary>     /// Entry point into console application.     /// </summary>     static void Main()     {       // Constructor is protected -- cannot use new       Singleton s1 = Singleton.Instance();       Singleton s2 = Singleton.Instance();       // Test for same instance       if (s1 == s2)       {         Console.WriteLine("Objects are the same instance");       }        // Wait for user       Console.ReadKey();     }   }    /// <summary>   /// The 'Singleton' class   /// </summary>   class Singleton   {     private static Singleton _instance;      // Constructor is 'protected'     protected Singleton()     {     }      public static Singleton Instance()     {       // Uses lazy initialization.       // Note: this is not thread safe.       if (_instance == null)       {         _instance = new Singleton();       }        return _instance;     }   } }

Output Objects are the same instance