Singleton Pattern

Singleton Pattern 

• a class only allow single instance of itself to be created.

• Not allow parameters to be specified when creating instance.(Problem when second request for an instance with different parameter)

• single constructor, private and no parameter.

• No sub classing (it may subclass more than 1 , subclass can create an instance)

public class SingletonTest

{

        private static readonly Lazy<SingletonTest> lazy =

                 new Lazy<SingletonTest>(() => new SingletonTest());

        public static SingletonTest Instance { get { return lazy.Value; } }

        public bool Test()

        {

            return true;

        }

        private SingletonTest()

        {

        }

}

//Calling SingleTon

private SingletonTest testsingle = SingletonTest.Instance;

protected void Page_Load(object sender, EventArgs e)

{

var test = testsingle.Test();

var test2 = SingletonTest.Instance.Test();

}

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Version 2 

public class CoffeeMachine

{

    private CoffeeMachine()

    {

    }

    public static CoffeeMachine _instance = null;

    public static CoffeeMachine Instance

    {

        get

        {

            if (_instance == null)

                _instance = new CoffeeMachine();

            return _instance;

        }

    }

}