C# INHERITANCE

One of the most important concepts in object-oriented programming is inheritance. Inheritance allows us to define a class in terms of another class, which makes it easier to create and maintain an application. This also provides an opportunity to reuse the code functionality and speeds up implementation time.

When creating a class, instead of writing completely new data members and member functions, the programmer can designate that the new class should inherit the members of an existing class. This existing class is called the base class, and the new class is referred to as the derived class.

Base and Derived Classes

A class can be derived from more than one class or interface, which means that it can inherit data and functions from multiple base classes or interfaces

using System;

namespace ConsoleApp1
{
    class Shape
    {
        public void setWidth(int w)
        {
            width = w;
        }
        public void setHeight(int h)
        {
            height = h;
        }
        protected int width;
        protected int height;
    }
    // Derived class
    class Rectangle : Shape
    {
        public int getArea()
        {
            return (width * height);
        }
    }

    class RectangleTester
    {
        static void Main(string[] args)
        {
            Rectangle Rect = new Rectangle();
            Rect.setWidth(5);
            Rect.setHeight(7);
            // Print the area of the object.
            Console.WriteLine("Total area: {0}", Rect.getArea());
            //Console.ReadKey();
        }
    }
}

Initializing Base Class

The derived class inherits the base class member variables and member methods. Therefore the super class object should be created before the subclass is created. You can give instructions for superclass initialization in the member initialization list.

using System;

namespace ConsoleApp1
{
    class Rectangle
    {
        //member variables
        protected double length;
        protected double width;
        public Rectangle(double l, double w)
        {
            length = l;
            width = w;
        }
        public double GetArea()
        {
            return length * width;
        }
        public void Display()
        {
            Console.WriteLine("Length: {0}", length);
            Console.WriteLine("Width: {0}", width);
            Console.WriteLine("Area: {0}", GetArea());
        }
    }//end class Rectangle 
    class Tabletop : Rectangle
    {
        private double cost;
        public Tabletop(double l, double w) : base(l, w)
        { }
        public double GetCost()
        {
            double cost;
            cost = GetArea() * 70;
            return cost;
        }
        public void Display()
        {
            base.Display();
            Console.WriteLine("Cost: {0}", GetCost());
        }
    }
    class ExecuteRectangle
    {
        static void Main(string[] args)
        {
            Tabletop t = new Tabletop(4.5, 7.5);
            t.Display();
            Console.ReadLine();
            //Length: 4.5
            //Width: 7.5
            //Area: 33.75
            //Cost: 2362.5
        }
    }
}

Multiple Inheritance in C#

C# does not support multiple inheritance. However, you can use interfaces to implement multiple inheritance. The following program demonstrates this:

using System;

namespace ConsoleApp1
{
    class Shape
    {
        public void setWidth(int w)
        {
            width = w;
        }
        public void setHeight(int h)
        {
            height = h;
        }
        protected int width;
        protected int height;
    }
    // Base class PaintCost
    public interface PaintCost
    {
        int getCost(int area);
    }
    // Derived class
    class Rectangle : Shape, PaintCost
    {
        public int getArea()
        {
            return (width * height);
        }
        public int getCost(int area)
        {
            return area * 70;
        }
    }
    class RectangleTester
    {
        static void Main(string[] args)
        {
            Rectangle Rect = new Rectangle();
            int area;
            Rect.setWidth(5);
            Rect.setHeight(7);
            area = Rect.getArea();
            // Print the area of the object.
            Console.WriteLine("Total area: {0}", Rect.getArea());
            Console.WriteLine("Total paint cost: ${0}", Rect.getCost(area));
            Console.ReadKey();
            //Total area: 35
            //Total paint cost: $2450
        }
    }
}