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Top 14 SOLID Principles Interview Questions and Answers

12/Dec/2023 | 10 minutes to read


Here is a List of essential SOLID Principles Interview Questions and Answers for Freshers and mid level of Experienced Professionals. All answers for these SOLID Principles questions are explained in a simple and easiest way. These basic, advanced and latest SOLID Principles questions will help you to clear your next Job interview.

SOLID Principles Interview Questions and Answers

These questions are targeted for Object-Oriented Design Principles like SOLID Principles, DRY, SoC, KISS etc. C# Programming language is used to show examples.

1. What are the SOLID Principles?

SOLID Principles is an acronym of 5 principles in Object Oriented Design (OOD). Robert C. Martin introduced these 5 principles in his 2000 paper "Design Principles and Design Patterns".

  • S - Single Responsibility Principle
  • O - Open Closed Principle
  • L - Liskov Substitution Principle
  • I - Interface Segregation Principle
  • D - Dependency Inversion Principle

1. Describe the Single Responsibility Principle (SRP).

In Object Oriented Programming, Single Responsibility (SRP) ensures that every module or class should be responsible for single functionality supported by the software system. In other words, Every class should have one and only reason to change it.
For example, In ASP.NET MVC HomeController class should be responsible related to Home Page functionality of software system.

3. Describe the Open Close Principle (OCP).

Open Close Principle (OCP) states or ensures that A class, component or entity should be open for extension but close for modification. In detail, We can extend any class via Interface, Inheritance or Composition whenever it's required instead of opening a class and modifying it's code.
For example, suppose you have implemented a functionality to calculate area of Rectangle and after some time you need to calculate the area of Square, then In this case you should not modify your original class code to add extra code for square. Instead you should create one base class initially and now you should extend this base class by your square class.

4. Explain Liskov Substitution Principle (LSP).

Liskov Substitution Principle (LSP) states that Objects in a program can be replaced by the instances of their subtypes without modifying the correctness of a program.
In other words, if A is subtype of B then instances of B may be replaced by the instances of A without altering the program correctness.

5. Explain Interface Segregation Principle (ISP).

Interface Segregation Principle (ISP) states that use many client specific interfaces instead of one general purpose interface.
In other words No client should be forced to implement other methods which it does not require. It means it's better to create a separate interface and allow your classes to implement multiple interfaces.

6. Explain the Dependency Inversion Principle (DIP).

12. How Design Principles are different from Design Patterns?

  • Design Principles are the core principles which we are supposed to follow while designing any software system on any platform using any programming language. Examples of Design Principles:
    • Dependency on abstraction not concrete classes
    • Encapsulate that varies
    • Program to interfaces not implementations
  • Design Patterns are the solutions to common occurring general problems, they are not exact program that can be fit to solve your problem rather you need to customize according to your problem. Design Patterns are already invented solutions which are well tested and safe to use. Examples of Design Patterns:
    • Single Design Pattern: When you want only one instance of a class.
    • Repository Design Pattern: To separate different layers of application (Business Repository, Data Repository)

7. What is Inversion of Control (IoC)?

Some Other Design Principles Interview Questions

8. What is 'Don't repeat yourself (DRY)' Principle?

DRY or 'Don't repeat yourself' is a software design principle that emphasizes on how to avoid the duplicate code in your codebase. and replace that redundant code with some less changing components like Abstraction . A redundant code creates problems like
  • You might have multiple files to apply similar code changes so it's time consuming.
  • Code readability is a big problem.
So the DRY principle helps you to solve these types of problems and allows you to write reusable, efficient code that provides better readability and maintainability. For more refer DRY Principle.

9. Explain the Separation of Concerns (SoC) design principle.

10. Explain KISS design principle.

KISS stands for "Keep It Simple, Stupid" means keep your logic simple that will be easy to maintain, and anyone can understand in future. Primary goal is simplicity of your code.

11. How Encapsulation works as a design Principle?

12. What is YAGNI Principle?

YAGINI principle states that "You Aren't Gonna Need It" means implement the functionality that you really need, not the functionality you think that "Just in some case we need them" or you should not implement the functionality that you are just presuming in future software needs. For more visit Yagni by Martin Fowler.

13. Good Understanding of SOLID Principles

It's a YouTube video explaining about SOLID Principles and Dependency Injection.

Some General Interview Questions for SOLID Principles

1. How much will you rate yourself in SOLID Principles?

When you attend an interview, Interviewer may ask you to rate yourself in a specific Technology like SOLID Principles, So It's depend on your knowledge and work experience in SOLID Principles.

2. What challenges did you face while working on SOLID Principles?

This question may be specific to your technology and completely depends on your past work experience. So you need to just explain the challenges you faced related to SOLID Principles in your Project.

3. What was your role in the last Project related to SOLID Principles?

It's based on your role and responsibilities assigned to you and what functionality you implemented using SOLID Principles in your project. This question is generally asked in every interview.

4. How much experience do you have in SOLID Principles?

Here you can tell about your overall work experience on SOLID Principles.


We have covered some frequently asked SOLID Principles Interview Questions and Answers to help you for your Interview. All these Essential SOLID Principles Interview Questions are targeted for mid level of experienced Professionals and freshers.
While attending any SOLID Principles Interview if you face any difficulty to answer any question please write to us at Our IT Expert team will find the best answer and will update on the portal. In case we find any new SOLID Principles questions, we will update the same here.