using System;

​

public class Program

{

    public static void Main()

    {

        SingletonCredentials c = SingletonCredentials.getInstance();

        c.method2();

        c.method1();

        c.method2();

        SingletonCredentials c2 = SingletonCredentials.getInstance();

        c2.method2();

        Credentials c3 = new Credentials();

        c3.method2();

        c3.method1();

        c3.method2();

        Credentials c4 = new Credentials();

        c4.method2();

        doSomething();

        doSomethingElse(c);

        doSomethingElse(c3);

    }

    public static void doSomething() {

        SingletonCredentials c = SingletonCredentials.getInstance();

        c.method2();

        Credentials c2 = new Credentials();

        c2.method2();

    }

    public static void doSomethingElse(AbstractCredentials c) {

        c.method2();

    }

}

​

public class SingletonCredentials : AbstractCredentials{

    private static SingletonCredentials instance;

    private SingletonCredentials() {}

    public static SingletonCredentials getInstance() {

        if (instance == null)

            instance = new SingletonCredentials();

        return instance;

    }

}

public abstract class AbstractCredentials {

    public string Val {get; protected set;}

    public void method1()

    {

        Val ="abc";

    }

    public void method2()

    {

        if(Val =="abc") {

            Console.WriteLine(Val);

        }

        else {

            Console.WriteLine("Val is not set");

        }

    }

}

​

​

public class Credentials : AbstractCredentials {

}

​

​