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.
The idea of inheritance implements the IS-A relationship. For example, mammal IS A animal, dog IS-A mammal hence dog IS-A animal as well, and so on.
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.
The syntax used in C# for creating derived classes is as follows −
<acess-specifier> class <base_class> {
   ...
}

class <derived_class> : <base_class> {
   ...
}

Consider a base class Shape and its derived class Rectangle −
using System;

namespace InheritanceApplication {
   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();
      }
   }
}
When the above code is compiled and executed, it produces the following result −
Total area: 35

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.
The following program demonstrates this −
using System;

namespace RectangleApplication {
   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();
      }
   }
}
When the above code is compiled and executed, it produces the following result −
Length: 4.5
Width: 7.5
Area: 33.75
Cost: 2362.5

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

namespace InheritanceApplication {
   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();
      }
   }
}
When the above code is compiled and executed, it produces the following result −
Total area: 35
Total paint cost: $2450


    119 Lectures 
     23.5 hours 

 Raja Biswas

    37 Lectures 
     13 hours 

 Trevoir Williams

    16 Lectures 
     1 hours 

 Peter Jepson

    159 Lectures 
     21.5 hours 

 Ebenezer Ogbu

    193 Lectures 
     17 hours 

 Arnold Higuit

    24 Lectures 
     2.5 hours 

 Eric Frick
 Print
 Add Notes
 Bookmark this page