C# | Multiple inheritance using interfaces

Last Updated : 06 Apr, 2023

Introduction:

Multiple inheritance refers to the ability of a class to inherit from multiple base classes. C# does not support multiple inheritance of classes, but it does support
multiple inheritance using interfaces. An interface is a collection of abstract methods that a class can implement to provide specific behavior. A class can
implement multiple interfaces, which allows it to inherit functionality from multiple sources.

Advantages:

Flexibility: Multiple inheritance using interfaces provides a flexible way to add functionality to a class without inheriting implementation details from a base class.
Code reuse: By implementing multiple interfaces, a class can reuse code from multiple sources, making it easier to write efficient and maintainable code.
Separation of concerns: Multiple inheritance using interfaces promotes the separation of concerns, making it easier to understand and maintain the code.

Disadvantages:

Complexity: Implementing multiple interfaces can make the code more complex and harder to understand, especially if there are a large number of interfaces or if they have complex relationships with each other.
Naming conflicts: Multiple inheritance using interfaces can lead to naming conflicts if two or more interfaces define methods or properties with the same name and signature.
Inconsistent behavior: If two or more interfaces define methods with the same name and signature but different behaviors, it can lead to inconsistent behavior in the class that implements them.

Sure, here’s an example code demonstrating multiple inheritance using interfaces in C#:

C#

   using System;
 
interface IShape
{
    double GetArea();
}
 
interface IColor
{
    string GetColor();
}
 
class Rectangle : IShape, IColor
{
    private double length;
    private double breadth;
    private string color;
 
    public Rectangle(double length, double breadth, string color)
    {
        this.length = length;
        this.breadth = breadth;
        this.color = color;
    }
 
    public double GetArea()
    {
        return length * breadth;
    }
 
    public string GetColor()
    {
        return color;
    }
}
 
class Program
{
    static void Main(string[] args)
    {
        Rectangle rect = new Rectangle(5, 10, "blue");
        Console.WriteLine("Area of rectangle: " + rect.GetArea());
        Console.WriteLine("Color of rectangle: " + rect.GetColor());
    }
}
 
  

Output

Area of rectangle: 50 Color of rectangle: blue

In this example, we have two interfaces: IShape and IColor. The Rectangle class implements both of these interfaces and provides its own implementation for the methods defined in the interfaces. The Program class creates an instance of the Rectangle class and calls its GetArea() and GetColor() methods.

The advantages of using multiple inheritance through interfaces include:

Allows a class to inherit from multiple sources, providing more flexibility in creating class hierarchies.
Interfaces enforce a contract that implementing classes must adhere to, promoting consistency and predictability in the codebase.
Interfaces allow for a separation of concerns, allowing for more modular and reusable code.

The disadvantages of multiple inheritance through interfaces include:

The need for more boilerplate code, as interfaces require implementing classes to provide their own implementation for each method.
Multiple inheritance can make the class hierarchy more complex and harder to understand.
Interfaces cannot contain any implementation, only method signatures, which may be limiting in some cases.

Some recommended reference books for learning more about multiple inheritance using interfaces in C# include:

C# 9.0 in a Nutshell: The Definitive Reference by Joseph Albahari and Ben Albahari
Pro C# 9 with .NET 5: With Visual Studio 2019 by Andrew Troelsen and Philip Japikse
C# 9 and .NET 5 – Modern Cross-Platform Development: Build intelligent apps, websites, and services with Blazor, ASP.NET Core, and Entity Framework Core
using Visual Studio Code by Mark J. Price.

Reference books:

“C# 9 and .NET 5 – Modern Cross-Platform Development: Build intelligent apps, websites, and services with Blazor, ASP.NET Core, and Entity Framework Core using Visual Studio Code, 5th Edition” by Mark J. Price
“C# in a Nutshell: The Definitive Reference” by Joseph Albahari and Ben Albahari
“Pro C# 9 with .NET 5: Comprehensively revised for Visual Studio 2019” by Andrew Troelsen and Philip Japikse.

In Multiple inheritance, one class can have more than one superclass and inherit features from all its parent classes. As shown in the below diagram, class C inherits the features of class A and B. But C# does not support multiple class inheritance. To overcome this problem we use interfaces to achieve multiple class inheritance. With the help of the interface, class C( as shown in the above diagram) can get the features of class A and B. Example 1: First of all, we try to inherit the features of Geeks1 and Geeks2 class into GeeksforGeeks class, then the compiler will give an error because C# directly does not support multiple class inheritance.

CSharp

   // C# program to illustrate
// multiple class inheritance
using System;
using System.Collections;
 
// Parent class 1
class Geeks1 {
 
    // Providing the implementation
    // of languages() method
    public void languages()
    {
 
        // Creating ArrayList
        ArrayList My_list = new ArrayList();
 
        // Adding elements in the
        // My_list ArrayList
        My_list.Add("C");
        My_list.Add("C++");
        My_list.Add("C#");
        My_list.Add("Java");
 
        Console.WriteLine("Languages provided by GeeksforGeeks:");
        foreach(var elements in My_list)
        {
            Console.WriteLine(elements);
        }
    }
}
 
// Parent class 2
class Geeks2 {
 
    // Providing the implementation
    // of courses() method
    public void courses()
    {
 
        // Creating ArrayList
        ArrayList My_list = new ArrayList();
 
        // Adding elements in the
        // My_list ArrayList
        My_list.Add("System Design");
        My_list.Add("Fork Python");
        My_list.Add("Geeks Classes DSA");
        My_list.Add("Fork Java");
 
        Console.WriteLine("\nCourses provided by GeeksforGeeks:");
        foreach(var elements in My_list)
        {
            Console.WriteLine(elements);
        }
    }
}
 
// Child class
class GeeksforGeeks : Geeks1, Geeks2 {
}
 
public class GFG {
 
    // Main method
    static public void Main()
    {
 
        // Creating object of GeeksforGeeks class
        GeeksforGeeks obj = new GeeksforGeeks();
        obj.languages();
        obj.courses();
    }
}
 
  

Runtime Error:

prog.cs(61, 30): error CS1721: `GeeksforGeeks’: Classes cannot have multiple base classes (`Geeks1′ and `Geeks2′) prog.cs(35, 7): (Location of the symbol related to previous error)

But we can indirectly inherit the features of Geeks1 and Geek2 class into GeeksforGeeks class using interfaces. As shown in the below diagram. Example 2: Both GFG1 and GFG2 interfaces are implemented by Geeks1 and Geeks2 class. Now Geeks1 and Geeks2 class define languages() and courses() method. When a GeeksforGeeks class inherits GFG1 and GFG2 interfaces you need not to redefine languages() and courses() method just simply create the objects of Geeks1 and Geeks2 class and access the languages() and courses() method using these objects in GeeksforGeeks class.

CSharp

   // C# program to illustrate how to
// implement multiple class inheritance
// using interfaces
using System;
using System.Collections;
 
// Interface 1
interface GFG1 {
    void languages();
}
 
// Parent class 1
class Geeks1 : GFG1 {
 
    // Providing the implementation
    // of languages() method
    public void languages()
    {
 
        // Creating ArrayList
        ArrayList My_list = new ArrayList();
 
        // Adding elements in the
        // My_list ArrayList
        My_list.Add("C");
        My_list.Add("C++");
        My_list.Add("C#");
        My_list.Add("Java");
 
        Console.WriteLine("Languages provided by GeeksforGeeks:");
        foreach(var elements in My_list)
        {
            Console.WriteLine(elements);
        }
    }
}
 
// Interface 2
interface GFG2 {
    void courses();
}
 
// Parent class 2
class Geeks2 : GFG2 {
 
    // Providing the implementation
    // of courses() method
    public void courses()
    {
 
        // Creating ArrayList
        ArrayList My_list = new ArrayList();
 
        // Adding elements in the
        // My_list ArrayList
        My_list.Add("System Design");
        My_list.Add("Fork Python");
        My_list.Add("Geeks Classes DSA");
        My_list.Add("Fork Java");
 
        Console.WriteLine("\nCourses provided by GeeksforGeeks:");
        foreach(var elements in My_list)
        {
            Console.WriteLine(elements);
        }
    }
}
 
// Child class
class GeeksforGeeks : GFG1, GFG2 {
 
    // Creating objects of Geeks1 and Geeks2 class
    Geeks1 obj1 = new Geeks1();
    Geeks2 obj2 = new Geeks2();
 
    public void languages()
    {
        obj1.languages();
    }
 
    public void courses()
    {
        obj2.courses();
    }
}
 
// Driver Class
public class GFG {
 
    // Main method
    static public void Main()
    {
 
        // Creating object of GeeksforGeeks class
        GeeksforGeeks obj = new GeeksforGeeks();
        obj.languages();
        obj.courses();
    }
}
 
  

Output:

Languages provided by GeeksforGeeks: C C++ C# Java  Courses provided by GeeksforGeeks: System Design Fork Python Geeks Classes DSA Fork Java

C# | Type.GetInterfaces() Method

ankita_saini

Improve

Article Tags :

C# | Multiple inheritance using interfaces

Introduction:

Advantages:

Disadvantages:

Sure, here’s an example code demonstrating multiple inheritance using interfaces in C#:

C#

The advantages of using multiple inheritance through interfaces include:

The disadvantages of multiple inheritance through interfaces include:

Some recommended reference books for learning more about multiple inheritance using interfaces in C# include:

Reference books:

CSharp

CSharp

Similar Reads