What is Object-Oriented Programming?
💡 Concept: Object-Oriented Programming (OOP)
Object-Oriented Programming (OOP) is a paradigm in C# that structures code around objects—self-contained units combining data and behavior. OOP helps organize large programs, promote reuse, and model real-world systems effectively.
📘 Quick Intro
OOP in C# focuses on designing software using classes and objects. It enables principles like encapsulation, inheritance, abstraction, and polymorphism—collectively called the four pillars of OOP.
🧠 Analogy
Imagine a car as an object. It has data (color, model) and behavior (drive, brake). You don't need to know how the engine works—just how to drive. OOP in C# works the same way: objects expose what they do and hide how they do it.
🔧 Technical Explanation
- 🔹 OOP encourages modularity by creating
classesas blueprints andobjectsas instances. - 🔹 Supports encapsulation to hide internal data and behavior using access modifiers.
- 🔹 Inheritance allows reuse of base class features in derived classes.
- 🔹 Polymorphism enables different implementations with a unified interface.
- 🔹 Abstraction separates interface from implementation for simplified interactions.
🎯 Use Cases
- ✔️ Designing reusable, maintainable components.
- ✔️ Modeling real-world entities (e.g., Users, Products).
- ✔️ Reducing code duplication through inheritance and interfaces.
- ✔️ Promoting team collaboration with clearly defined class responsibilities.
💻 Real Code Example
public class Animal
{
public string Name { get; set; }
public virtual void Speak()
{
Console.WriteLine("Animal speaks");
}
}
public class Dog : Animal
{
public override void Speak()
{
Console.WriteLine("Dog barks");
}
}
❓ Interview Q&A
Q1: What is Object-Oriented Programming?
A: A design approach where software is built using objects that encapsulate data and behavior.
Q2: What are the four pillars of OOP?
A: Encapsulation, Inheritance, Abstraction, and Polymorphism.
Q3: What is encapsulation?
A: Hiding internal object data using access modifiers like private and public.
Q4: What is inheritance in C#?
A: It's a mechanism to derive new classes from existing ones.
Q5: Define abstraction in C#.
A: Showing essential features while hiding internal implementation.
Q6: What is polymorphism?
A: The ability for methods to behave differently based on the object type.
Q7: What is the base class for all types in C#?
A: System.Object
Q8: How does OOP promote reuse?
A: Through inheritance and modular class design.
Q9: Can C# classes implement multiple interfaces?
A: Yes, but can inherit only one class.
Q10: How do you achieve abstraction in C#?
A: Using abstract classes and interfaces.
📝 MCQs
Q1. What is the main principle behind OOP?
- Flat functions
- Global variables
- Objects encapsulate data and behavior
- Sequential programming
Q2. Which is NOT a pillar of OOP?
- Encapsulation
- Inheritance
- Compilation
- Abstraction
Q3. Which access modifier hides class data?
- public
- internal
- private
- protected
Q4. Can a class inherit multiple classes in C#?
- Yes
- No
- Only sealed
- If partial
Q5. What is used to achieve polymorphism?
- sealed
- readonly
- virtual and override keywords
- params
Q6. What is the purpose of an abstract class?
- Used in static methods
- Cannot be inherited
- Provide a base with optional implementation
- None
Q7. What is a real-world analogy for encapsulation?
- Glass jar
- Capsule hiding medicine
- Open book
- None
Q8. What is System.Object?
- Static class
- Base for interfaces
- Root of all C# types
- Only for collections
Q9. How does OOP help large teams?
- Creates fewer files
- Avoids testing
- Encourages modular reusable code
- Prevents bugs
Q10. What is true about classes?
- They store only static data
- They define object structure and behavior
- They are obsolete
- None of these
💡 Bonus Insight
Object-oriented programming provides the foundation for most modern applications and frameworks. Understanding how to structure code using classes, interfaces, and design principles is key to mastering C# development.
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