Singleton

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 UML:

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SAMPLE:

 

 1     class SingletonClient
 2     {
 3         static void Main(string[] args)
 4         {
 5             Singleton singleton = Singleton.getInstance();
 6             singleton.SaySomething();
 7 
 8             // Wait for user
 9              Console.ReadKey();
10         }
11     }
12 
13     #region Singleton
14 
15     public class Singleton 
16     {
17         private volatile static Singleton _uniqueInstance;
18         private static readonly object _syncLock = new object();
19  
20         private Singleton() {}
21  
22         public static Singleton getInstance() 
23         {
24             if (_uniqueInstance == null) 
25             {
26                 // Lock area where instance is created
27                  lock(_syncLock)
28                 {
29                     if (_uniqueInstance == null) 
30                     {
31                         _uniqueInstance = new Singleton();
32                     }
33                 }
34             }
35             return _uniqueInstance;
36         }
37 
38         public void SaySomething()
39         {
40             Console.WriteLine("I am double checked, therefore I am");
41         }
42     }