SOLID principles are a set of five important guidelines in software design that help developers create more maintainable and flexible code.
Each principle focuses on a different aspect of writing good software. A break down of each principle in simple terms, is as follows:
- Single Responsibility Principle (SRP):
Imagine you’re building a house. The Single Responsibility Principle suggests that each worker should have a specific job. In code, it means that a class should have just one main job or responsibility. If you’re making a C# program to manage books, you’d have a class for managing books and another for displaying them. This way, if something changes in one area, it won’t affect the other unnecessarily. - Open/Closed Principle (OCP):
Think of a puzzle piece that fits perfectly into a slot. The Open/Closed Principle tells us that our code should be like that puzzle piece – open for extension but closed for modification. In C#, it means that you should design your classes so that you can add new features without changing the existing code. If you’re creating shapes, you’d create a base shape class and then extend it to add new shapes, without changing how the existing shapes work. - Liskov Substitution Principle (LSP):
Imagine a remote control for a TV. You’d expect that any remote control works seamlessly with any TV. In code, the Liskov Substitution Principle states that objects of a derived class should be able to replace objects of the base class without affecting the program’s correctness. In C#, if you have a base class for animals and derived classes for cats and dogs, you’d want to be able to treat them as animals interchangeably without breaking anything. - Interface Segregation Principle (ISP):
Picture a menu in a restaurant – it only lists dishes from a specific category. The Interface Segregation Principle suggests that classes should not be forced to implement interfaces they don’t need. In C#, if you’re creating a reporting system with multiple report types, you’d create separate interfaces for each report type, so that a class implementing one report doesn’t have to implement unnecessary methods from other report types. - Dependency Inversion Principle (DIP):
Think of a plug and socket – they fit together regardless of whether the power source is a generator or a power plant. The Dependency Inversion Principle says that high-level modules (like your main application logic) should not depend on low-level modules (like specific implementations). Instead, they should both depend on abstractions (like interfaces or abstract classes). In C#, if you’re creating a logging system, your main application shouldn’t directly depend on a specific logging library; it should depend on an abstraction that various logging libraries can implement.
These principles might seem a bit abstract at first, but applying them to C# code can lead to software that’s easier to understand, maintain, and adapt as projects evolves.