Hello friends,
All of you must be aware of what Singleton Design Pattern is. Just to define it in one line, It is a pattern which allows creation of one and only instance of a class.
The practical scenario where you can go with this pattern is having a print job class instance, single running instance of an application etc.
The best example is Google Talk desktop application.
Let us try to implement this pattern via C# code.
The Singleton class above will be instantiated only once.
When the GetInstance is called, it will return the statically created instance of the class.
All of you must be aware of what Singleton Design Pattern is. Just to define it in one line, It is a pattern which allows creation of one and only instance of a class.
The practical scenario where you can go with this pattern is having a print job class instance, single running instance of an application etc.
The best example is Google Talk desktop application.
Let us try to implement this pattern via C# code.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 | using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace DesignPatternsDemo { public class SingletonClass { private SingletonClass() { } //Implementation #1 //static SingletonClass _instance = null; //public static SingletonClass GetInstance() //{ // if (_instance == null) // { // _instance = new SingletonClass(); // } // return _instance; //} //Implementation #2 //Be aware that in a multithreaded program, different threads could try //to instantiate a class simultaneously. For this reason, a Singleton //implementation that relies on an if statement to check whether the //instance is null will not be thread-safe. Do not use code like that! static readonly SingletonClass _instance = new SingletonClass(); public static SingletonClass GetInstance { get { return _instance; } } public string GetWelcomeMessage() { return "Welcome to the Singleton world!! "; } } } |
The Singleton class above will be instantiated only once.
When the GetInstance is called, it will return the statically created instance of the class.
Is this implementation Thread-safe?
ReplyDeletestatic SingletonClass _instance = null;
static object lockThis;
public static SingletonClass GetInstance()
{
lock(lockThis)
{
if (_instance == null)
_instance = new SingletonClass();
}
return _instance;
}
Yes that implementation is thread safe.
ReplyDelete