Singleton class in C#.NET

In the article we will discuss about singleton class in C#.NET.

Definition:

“A class which can be instantiated only once is called singleton class”.

The term singleton is derived from the mathematics concept of a singleton. Singleton is set with only one element. E.g.: Set {0} is a singleton.

How to achieve singleton class?

• Mark the constructor as private so that outside the class it’s not possible to create instance of the class.
• Create static/Shared method can be added to the class to create instance of the class and return the reference of the object.

Example:

class SingletonClass     {         private static Singlet

onClass obj;

        public int tempVal

        {

            get; set;

        }

        //private constuctor

        private 

SingletonClass()

        {

        }

        public static Singleto

nClass GetInstance()

        {

            if (obj == null)

            {

                obj = new Sing

letonClass();                

            }

            return obj;

        }

    }

    class SingletonClassProgra

m

    {

        public static void 

Main(string[] args)

        {

            SingletonClass 

obj1,obj2;

            //obj1=new 

SingletonClass(); //invlid 
due to constructore is private. Error as inaccissible due to protection level

             obj1=SingletonCla

ss.GetInstance();

            obj1.tempVal =20;

            obj2=SingletonClas

s.GetInstance();

            Console.WriteLine(

" /********* singleton class 
Example **********/");

            Console.WriteLine(

"variable value is {0}",obj2.
tempVal); //value is 20 because both obj1,obj2 are referring to same object

            Console.Read();

        }

    }

Output:

Data points:

• Singleton is a design pattern in software development.
• Singleton class is like a sealed class