In Object Oriented Programming language, a class or an object can inherit features and characteristics of one or more parent object or class. It is used when a sub class needs to access the some or all the properties of a parent class. It is also useful when the child class needs to combine multiple contracts of a base class. C++ allows the provision of having multiple inheritance in sub classes.
Why is multiple inheritance not allowed in C#?
In C#, a child class can only have a one-parent class as the designers of this language wanted to keep the class hierarchy simple by restricting the implementation of multiple inheritance.
Work around to implement multiple inheritance in C#
There are several ways to achieve the functionality of multiple inheritance in C# language. The most famous and easy method is to use the combination of interfaces.
using System;
using System.Collections;
// Parent or Base Class A
public class ProgrammingLanguage {
// Providing the implementation of programming languages() method
public void GetProgrammingLanguages()
{
// create an arraylist
ArrayList list = new ArrayList();
// add items in list
list.Add("C#");
listAdd("C++");
list.Add("C");
list.Add("Java");
list.Add("Python");
// print item in the language list
foreach(var item in list )
{
Console.WriteLine("\n");
Console.WriteLine(item);
}
}
}
// Parent or Base Class B
public class Course {
public void GetCourses()
{
// create a list for courses
ArrayList list = new ArrayList();
// add items in course list
list.Add("Database Architecture");
list.Add("Object Oriented Programming");
list.Add("Management Information System");
list.Add("Automata Theory");
list.Add("Introduction to Programming");
// print items in course list
foreach(var item in list)
{
Console.WriteLine("\n");
Console.WriteLine(item);
}
}
}
// Child or Sub class to inherit one or more classes
public class Enrollment : ProgrammingLanguage, Course {
}
// Adding Main Class
public class Program {
// Main method
public static public void Main()
{
// Creating an object of Enrollment class
Enrollment objEnrollment = new Enrollment ();
objEnrollment.GetProgrammingLanguages();
objEnrollment.GetCourses();
}
}
The above program will throw a runtime exception of ‘Classes cannot have multiple base classes’. The following program is used to implement multiple class inheritance using interfaces in C#
using System;
using System.Collections;
// Create Interface for the class Programming Language
public interface IProgrammingLanguage {
public void GetProgrammingLanguages ();
}
// Parent Class A ProgrammingLanguage
public class ProgrammingLanguage : IProgrammingLanguage {
// Providing the implementation of programming languages() method
public void GetProgrammingLanguages()
{
// create an arraylist
ArrayList list = new ArrayList();
// add items in list
list.Add("C#");
listAdd("C++");
list.Add("C");
list.Add("Java");
list.Add("Python");
// print item in the language list
foreach(var item in list )
{
Console.WriteLine("\n");
Console.WriteLine(item);
}
}
}
// Create Interface for the class Courses
public interface ICourses{
public void GetCourses ();
}
// Parent Class B Course
public class Course {
public void GetCourses()
{
// create a list for courses
ArrayList list = new ArrayList();
// add items in course list
list.Add("Database Architecture");
list.Add("Object Oriented Programming");
list.Add("Management Information System");
list.Add("Automata Theory");
list.Add("Introduction to Programming");
// print items in the course list
foreach(var item in list)
{
Console.WriteLine("\n");
Console.WriteLine(item);
}
}
}
// Child or Sub class to inherit both interfaces ProgrammingLanguage and Course
public class Enrollment : IProgrammingLanguage, ICourse {
// Creating objects of ProgrammingLanguage and Course class
IProgrammingLanguage objA = new ProgrammingLanguage ();
ICourse objB = new Course ();
public void GetProgrammingLanguages()
{
objA.GetProgrammingLanguages ();
}
public void GetCourses()
{
objB.GetCourses();
}
}
// Adding Main Class to print the result
public class Program {
// main method
public static public void Main()
{
// Creating an object of Enrollment class
Enrollment objEnrollment = new Enrollment ();
// access the methods
Console.WriteLine("\n The following Programming Languages are available: \n ");
objEnrollment.GetProgrammingLanguages();
Console.WriteLine("\n \n The following Courses are available: \n ");
objEnrollment.GetCourses();
}
}
Output of the above code
The Following Programming Languages are available:
C#
C++
C
Java
Python
The following Courses are available:
Database Architecture
Object Oriented Programming
Management Information System
Automata Theory
Introduction to Programming
Conclusion
Inheritance is one of the main pillar of Object Oriented Programming as it allows the class to be defined in a hierarchical manner. It increase the reusability of the code, thus saving time and effort of a developer by extending the software code. Inheritance is ‘is-a’ relationship between children and parent. In C#, single inheritance is allowed only but multiple inheritance can be achieved by using one or multiple interfaces simultaneously. Another advantage of using interfaces is hiding the implementation of a class from outside world.
