Principles of SOLID in .NET Development

Question

Can anyone explain what are solid principles with .NET development?

Jaish Mathews · Answer

The SOLID principles are a set of design principles aimed at creating robust maintainable and scalable software. They are especially relevant in object-oriented programming and are widely adopted in .NET development. Here's an overview of the SOLID principles: Below are the details I consolidated from multiple sources. 1. Single Responsibility Principle (SRP) Definition: A class should have only one reason to change. Each class or module should focus on a single functionality or responsibility. Ensures better maintainability and reduces the risk of changes in one part affecting unrelated parts. Example in .NET: public class InvoiceGenerator { public void GenerateInvoice(Order order) { // Logic to generate an invoice } } public class EmailNotifier { public void SendInvoiceEmail(Invoice invoice) { // Logic to send invoice email } } Here invoice generation and notification are handled by separate classes. 2. Open/Closed Principle (OCP) Definition: Software entities (classes modules functions) should be open for extension but closed for modification. Code should allow new functionality without altering existing code. Achieved through abstraction interfaces and inheritance. Example in .NET: public interface ILogger { void Log(string message); } public class FileLogger : ILogger { public void Log(string message) { // Logic to log to a file } } public class DatabaseLogger : ILogger { public void Log(string message) { // Logic to log to a database } } public class LoggerService { private readonly ILogger _logger; public LoggerService(ILogger logger) { _logger = logger; } public void LogMessage(string message) { _logger.Log(message); } } New loggers can be added without modifying LoggerService . 3. Liskov Substitution Principle (LSP) Definition: Objects of a superclass should be replaceable with objects of a subclass without affecting the correctness of the program. Subtypes must maintain the behavior of their parent types. Example in .NET: public class Rectangle { public virtual int Width { get; set; } public virtual int Height { get; set; } public int GetArea() => Width * Height; } public class Square : Rectangle { public override int Width { set { base.Width = base.Height = value; } } public override int Height { set { base.Width = base.Height = value; } } } In this example Square overrides behavior to ensure it can substitute Rectangle without breaking functionality. 4. Interface Segregation Principle (ISP) Definition: A class should not be forced to implement interfaces it doesn't use. Split large interfaces into smaller specific ones tailored to the needs of clients. Example in .NET: public interface IPrinter { void Print(); } public interface IScanner { void Scan(); } public class MultiFunctionPrinter : IPrinter IScanner { public void Print() { // Print logic } public void Scan() { // Scan logic } } public class BasicPrinter : IPrinter { public void Print() { // Print logic } } Here BasicPrinter doesn't need to implement IScanner . 5. Dependency Inversion Principle (DIP) Definition: High-level modules should not depend on low-level modules. Both should depend on abstractions. Depend on interfaces or abstract classes not concrete implementations. Example in .NET: public interface IDataAccess { void LoadData(); } public class DatabaseAccess : IDataAccess { public void LoadData() { // Logic to load data from database } } public class FileAccess : IDataAccess { public void LoadData() { // Logic to load data from a file } } public class BusinessLogic { private readonly IDataAccess _dataAccess; public BusinessLogic(IDataAccess dataAccess) { _dataAccess = dataAccess; } public void ProcessData() { _dataAccess.LoadData(); } } The BusinessLogic class depends on the IDataAccess interface allowing flexible implementations. Why Use SOLID Principles in .NET Development? Maintainability: Easier to update and manage code. Scalability: Supports growth with minimal changes to existing code. Testability: Simplifies unit testing with decoupled components. Reusability: Encourages reusable and modular code components. Collaboration: Improves team productivity by reducing complexity. By adhering to SOLID principles .NET developers can create applications that are more robust modular and easier to work with over time. You can accept this answer if this helps.

Jaish Mathews · Answer

OOPS is programming paradigm based on the concept of objects that contain data (fields) and code (methods). SOLID is design principles aimed at improving the maintainability scalability and flexibility of software. Object-Oriented Programming (OOP) is the foundational paradigm upon which SOLID principles are built. Also Singleton is a design pattern not part of SOLID. Dependency Injection (DI) is a technique that helps implement the Dependency Inversion Principle (DIP)  one of the SOLID principles. I recommend referencing multiple documents to ensure all aspects are thoroughly understood. Becasue here can't cover all these.

Kiran Kumar · Answer

Hi Mathew I am fine with your suggestion that SOLID is different from Pattrens I have analyzed each individual principle and find few observations If you closely look at the OCP ISP and IDP the code looks same so why it is similar code except IDP has multiple inheritance the remaining everything same right I Agree that it is a principle we have to go with programming logic designed by Microsoft but just to confirm are these 3 principles specific to interface based implementation

Kiran Kumar · Answer

Hi Mathew Thanks for the detail explanations I think I need to go one by one and implement that in real time features  I will let you know if need any clarification First I go with SRP principle Before going into it I need a few clarifications I know the OOPS concepts so how different it from four object principles that I know  As I can see in the title you mentioned these are relevant to OOPS however can explain if you have details little more relation with oops principles Also I know Singleton pattern and DI (I think you mentioned it as DIP inversion) in my project experience so just want to know is that SOLID pattern or principles Please clarify to get a better idea about these principles