Understanding liskov principle c# | liskov substitution principle c# example

Liskov substitution principle c# example : In this blog post, we’ll dive deep into the Liskov Principle in c#, explore its importance, and provide a comprehensive C# example to illustrate its application. The Liskov Substitution Principle (LSP) is a fundamental concept in object-oriented programming and one of the SOLID principles. Understanding and applying LSP can lead to more robust and maintainable code.

What is the Liskov Substitution Principle?

The Liskov Substitution Principle, introduced by Barbara Liskov in 1987, is defined as follows:

If S is a subtype of T, then objects of type T may be replaced with objects of type S (i.e., an object of a subclass) without altering the desirable properties of the program (correctness, task performed, etc.).

In simpler terms, LSP states that subclasses should be substitutable for their base classes without causing unexpected behavior in the program. This principle ensures that derived classes extend the functionality of base classes without changing their original behavior.

Importance of Liskov Substitution Principle c#

Adhering to the Liskov Substitution Principle brings many benefits:

  1. Improved Code Reusability: By ensuring that subclasses can be used interchangeably with base classes, code becomes more flexible and reusable.
  2. Enhanced Maintainability: Following LSP leads to a more predictable and understandable codebase, making it easier to maintain and extend.
  3. Increased Robustness: Adhering to LSP minimizes the risk of introducing bugs when subclasses are used in place of base classes.

Liskov Substitution Principle in C#

To illustrate the Liskov Substitution Principle in C#, let’s consider a classic example involving a base class and its derived classes.

Here you can learn about Difference Between Async and Await in C# with Example which is created by csharpmaster.

Example Scenario: Shapes and Areas

Let’s create a base class Shape and two derived classes, Rectangle and Square. We’ll demonstrate how adhering to LSP ensures that our code remains correct and predictable.

liskov substitution principle c# example
liskov substitution principle c# example

In this example, both Rectangle and Square classes inherit from the Shape base class and override the Area method. According to LSP, we should be able to use instances of Rectangle and Square interchangeably where a Shape is expected.

Read csharp master’s best tutorial design patterns in c# with example.

Applying Liskov Substitution Principle

Let’s write a method that calculates the total area of a list of shapes:

liskov principle c#
liskov principle c#

We can now create a list of shapes and calculate the total area without worrying about the specific types of shapes in the list:

liskov substitution principle c#
liskov substitution principle c#

The CalculateTotalArea method works seamlessly with both Rectangle and Square instances, demonstrating the proper application of the Liskov Substitution Principle.

Violating Liskov Substitution Principle

To understand the consequences of violating LSP, let’s modify the Square class to inherit from Rectangle instead of Shape:

C# Liskov Substitution Principle
C# Liskov Substitution Principle

In this modified Square class, the Width and Height properties are overridden to ensure that both dimensions remain equal. However, this violates LSP because a Square can no longer be substituted for a Rectangle without altering the expected behavior:

example of liskov substitution principle c#
example of liskov substitution principle c#

The above code will output:

Output of Liskov Substitution Principle
Output of Liskov Substitution Principle

This result is unexpected because changing the width of a rectangle should not affect its height. This violation of LSP can lead to bugs and unpredictable behavior in the program.

Ensuring Compliance with Liskov Principle c#

To ensure that your code complies with LSP, consider the following guidelines:

  1. Avoid Overriding Base Class Methods Incorrectly: Ensure that overridden methods in derived classes maintain the expected behavior of the base class methods.
  2. Use Abstract Classes and Interfaces Wisely: Define clear contracts using abstract classes and interfaces, ensuring that derived classes adhere to these contracts.
  3. Test Substitutability: Regularly test your subclasses to ensure they can be used in place of base classes without causing unexpected behavior.


The Liskov Substitution Principle is a crucial aspect of object-oriented programming that promotes code reusability, maintainability, and robustness. By understanding and applying LSP in your C# code, you can create more reliable and flexible software. Remember to design your subclasses in a way that they can be substituted for their base classes without altering the expected behavior of your program.

By following the guidelines and examples provided in this post, you can ensure that your code adheres to the Liskov Substitution Principle, resulting in a more maintainable and predictable codebase.

By focusing on real-world examples and practical applications, this blog post aims to provide a thorough understanding of the Liskov Substitution Principle in C#. Whether you’re a seasoned developer or just starting, adhering to LSP can significantly improve the quality of your code.

Leave a Reply

Your email address will not be published. Required fields are marked *