// Author : Tech Point Fundamentals

// Website : www.techpointfunda.com

// Demo : Abstract Class versus Interface in C# 8

​

using System;

public class Program

{

    interface IBaseInterface

    {

        public abstract void Display();

        public static void Print() 

        { 

            Console.WriteLine("This is interface static method"); 

        }

        public virtual void Show() // Default interface method

        {

            Console.WriteLine("This is interface virtual method");

        }           

    }

    interface IDerivedInterface : IBaseInterface

    {

        abstract void IBaseInterface.Show(); // Abstract Override : Re-abstraction

    }

    abstract class AbstractClass 

    {

        public int globalVariable = 0;      

        public abstract void Display(); 

        public static void Print() 

        { 

            Console.WriteLine("This is abstract class static method"); 

        }

        public virtual void Show()

        {

            Console.WriteLine("This is abstract class virtual method");

        }   

        public AbstractClass() // Abstract class constructor

        {

            this.globalVariable = 100;

        }

         ~ AbstractClass() // Abstract class destructor

        {

            Console.WriteLine("Abstract class destructor is called");

        }

    }

    struct MyStructor : IBaseInterface

    {       

        public void Display()

        {

            Console.WriteLine("This is implemented method of interface in MyStructor");

        }       

        void IBaseInterface.Show() // Explicit Override

        {

            Console.WriteLine("This is overriden interface virtual method in MyStructor");

        }   

    }

​

    class DerivedClass : IBaseInterface

    {

        public void Display()

        {

            Console.WriteLine("This is implemented method in DerivedClass");

        }   

        void IBaseInterface.Show() // Explicit Override

        {

            Console.WriteLine("This is overriden interface virtual method in DerivedClass");

        }   

    }

    class ChildClass : AbstractClass

    {

        public sealed override void Display() // // Sealed Override

        {

            Console.WriteLine("This is overridden abstract method in ChildClass");

        }   

        public new void Show() // Virtual Method Hiding

        {

            Console.WriteLine("This is hidden abstract class virtual method in ChildClass");

        }

    }

    abstract class SubClass : AbstractClass

    {

        public override abstract void Display(); // Abstract Override in abstract class

    }

    abstract class MyClass : IBaseInterface

    {

        public abstract void Display(); // Re-abstraction of interface member in abstract class

        public abstract void Show();

    }

    public static void Main()

    {

        Console.WriteLine("------------- Struct Inheriting Interface-----------------\n");

        MyStructor _myStruct = new MyStructor();

        _myStruct.Display();

        ((IBaseInterface)_myStruct).Show(); // interface virtual methods are not inherited in the struct so they can only be called with interface type reference variable

        IBaseInterface.Print(); // Static method called with interface name

        Console.WriteLine("\n------------- Class Inheriting Interface-----------------\n");

        DerivedClass _derivedClass = new DerivedClass();

        _derivedClass.Display();

        ((IBaseInterface)_derivedClass).Show(); // interface virtual methods are not inherited in the class so they can only be called with interface type reference variable

        IBaseInterface.Print(); // Static method called with interface name

        Console.WriteLine("\n------------- Class Inheriting Abstract Class-----------------\n");        

        ChildClass _childClass = new ChildClass();

        _childClass.Display();

        _childClass.Show();  // abstract class virtual methods are inherited in the class

        ((AbstractClass)_childClass).Show(); // base abstract class virtual methods will be called

        ChildClass.Print(); // Static method called with class name

    }

}