// Author   : Tech Point Fundamentals

// Website  : www.techpointfunda.com

// YouTube  : https://www.youtube.com/c/TechPointFundamentals

// Demo     : Covariant Return Type in C# 9

​

using System;

​

class GrandFather : Object

    {

        public int Id { get; set; }

        public string Name { get; set; }

​

        public virtual void Show()

        {

            Console.WriteLine("GrandFather Class Show() method is called.");

        }

    }

​

    class Father: GrandFather

    {

        public int Age { get; set; }

        public string City { get; set; }

​

        public void Display(GrandFather grandFather)

        {

            Console.WriteLine("Father Class Display() : " + grandFather.GetType().ToString());

        }

​

        // This method can return instance of Father and Child also

        public virtual GrandFather Print(string type = "")

        {

            if (type.ToUpper() == "F")

                return new Father();

            else if (type.ToUpper() == "C")

                return new Child();

            else

                return new GrandFather();

        }

​

        public override void Show()

        {

            Console.WriteLine("Father Class Show() method is called.");

        }

    }

​

    class Child: Father

    {

        public int Gender { get; set; }

        public string DOB { get; set; }

​

        public override void Show()

        {

            Console.WriteLine("Child Class Show() method is called.");

        }

        //  Here the return type is changed to Father instead of GrandFather

        public override Father Print(string type = "")

        {

            if (type.ToUpper() == "F")

                return new Father();

            else if (type.ToUpper() == "C")

                return new Child();

            else

                return null;

        }

    }

public class Program

{

    public static void Main()

    {

            Father father = new Father();

​

            father.Display(new Child());

            father.Display(new Father());

            father.Display(new GrandFather());

​

            (father.Print()).Show();

            (father.Print("F")).Show();

            (father.Print("C")).Show();

    }

}