Singleton
The Singleton Design Pattern ensures that only a single instance of a given object can exist.
It does this by making the class constructor private so that it [the singleton itself] has full control over when the class instance is created. In order to gain access to an instance of a class that implements the Singleton pattern, the developer must call a shared/static method of that Singleton class.
A VB example of a Singleton
Public Class SingletonSample
'shared members
Private Shared _instance As New SingletonSample
Public Shared Function Instance() As SingletonSample
Return _instance
End Function
'instance members
Private Sub New()
'public instantiation disallowed
End Sub
'other instance members
'...
End Class
A C# example of a Singleton
public class SingletonSample
{
//shared members
private static SingletonSample _instance = new SingletonSample();
public static SingletonSample Instance()
{
return _instance;
}
//instance members
private SingletonSample()
{
//public instantiation disallowed
}
//other instance members
//...
}
With the Singleton Design Pattern in place, the developer can easily access that single object instance without needing to worry about inadvertently creating multiple instances.
VB - Dim mySingleton As SingletonSample = SingletonSample.Instance
C# - SingletonSample mySingleton = SingletonSample.Instance();
Revision number 7, Thursday, November 13, 2008 10:51:14 PM by raklos
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Fri, Mar 28, 2008 8:25 AM
by kulanthaivelu
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Good Article. Now I got basic idea about singleton pattern. Thanks
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Fri, Apr 11, 2008 1:40 AM
by shariff
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cool!!!, thanks for the info, really helps me to understand SINGLETON.
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Fri, Jun 13, 2008 4:34 PM
by dragthor
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Is this thread safe?
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Sun, Jun 15, 2008 7:46 PM
by mbanavige
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since the singleton is created via a static initializer, its creation is thread-safe.
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Fri, Aug 8, 2008 4:39 AM
by ojosdegris
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sorry, have you looked at this, before writing this article? http://msdn.microsoft.com/en-us/library/ms954629.aspx sealed class Singleton { private Singleton() {} public static readonly Singleton Instance = new Singleton();
} i think it's better way to implement singleton in C#
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Thu, Dec 11, 2008 2:14 AM
by ashrafur
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Nice one.
Described basic idea very clearly.
But developer need to aware about Thread Safe so need to use Locking. Here is a complete example with a description of Thread safe, Synchronous call and Locking.
http://ashrafur.wordpress.com/2008/08/13/singleton-instantiate-just-one-object/
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Thu, Dec 11, 2008 9:58 PM
by mbanavige
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Locking is not required as the singleton object in the example was instantiated via a static initializer. The .NET framework guarantees that static initializers are run exactly once. On the other hand, the synclock double-check pattern might appear to be a good pattern but can actually still intermittently create multiple objects due to processor optimizations.
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Thu, Dec 18, 2008 3:17 AM
by sirdneo
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HOw to implement multi lock version of singeltoin
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Mon, Apr 13, 2009 6:34 AM
by zimmybansal
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Nice article for understanding basic implementation of Singleton! Congratz!!!
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Fri, Apr 17, 2009 3:00 PM
by joseluis2411
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good article
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