Preparing for a .NET Developer Interview: Key Concepts and Questions

Administration / 4 Dec, 2022

If you're preparing for a .NET developer interview, understanding the core concepts and common questions is crucial. Below is a guide to some of the most important topics and questions you might encounter during your interview.

1. What is OOP (Object-Oriented Programming)?

• Question: Define OOP and explain why it is used.

• Answer: OOP is a programming paradigm based on the concept of "objects," which are instances of classes. It is used to create real-world applications with dynamic memory allocation and modern features like data abstraction, encapsulation, polymorphism, and inheritance. OOP helps in building secure and reusable code.

2. Pillars of OOP

• Question: What are the pillars of OOP?

• Answer: The four pillars of OOP are:

  1. Data Abstraction

  2. Encapsulation

  3. Polymorphism

  4. Inheritance

3. Difference Between Class and Object

• Question: What is the difference between a class and an object?

• Answer:

  • Class: A blueprint or template for creating objects. It defines the characteristics and behaviors of the object.

  • Object: An instance of a class with identity, state, and behavior.

4. Components Defined Under a Class

• Question: What components can be defined under a class in C#?

• Answer: In C#, a class can have:

  1. Data members (variables)

  2. Methods (member functions)

  3. Properties

  4. Constructors

  5. Inner classes

  6. User-defined objects (like ArrayList)

5. What is Data Encapsulation?

• Question: Define data encapsulation and explain its implementation.

• Answer: Data encapsulation is the concept of hiding the internal state and requiring all interactions to be performed through an object's methods. This is achieved by making data members private or protected and providing public methods for access.

  • Implementation:

    1. Using properties with getters and setters.

    2. Using constructors.

    3. Using methods.

6. Difference Between Data Encapsulation and Data Abstraction

• Question: What is the difference between data encapsulation and data abstraction?

• Answer:

  • Data Encapsulation: Hiding the internal state of an object and only allowing access through public methods.

  • Data Abstraction: Hiding the implementation details and showing only the functionality to the user. Achieved using interfaces and abstract classes.

7. Role of Interfaces and Abstract Classes

• Question: Why do we create interfaces and abstract classes?

• Answer:

  • Interface: Used to achieve data abstraction and define a contract for what a class can do without dictating how it should do it.

  • Abstract Class: Allows defining methods that must be implemented by derived classes. It can contain both abstract and concrete methods, but cannot be instantiated.

8. Design Patterns

• Question: What are design patterns and why are they important?

• Answer: Design patterns are standard solutions to common problems in software design. They provide a template for how to solve problems in different situations. Examples include Abstract Factory, Factory Method, Singleton, etc.

9. Polymorphism

• Question: What is polymorphism and what are its types?

• Answer: Polymorphism allows objects to be treated as instances of their parent class rather than their actual class. There are two types:

  1. Compile-time Polymorphism (Method Overloading)

  2. Runtime Polymorphism (Method Overriding)

10. Inheritance

• Question: What is inheritance and what are its types?

• Answer: Inheritance allows a class to inherit properties and methods from another class. It promotes code reusability and a hierarchical classification. Types include:

  1. Single Inheritance

  2. Multilevel Inheritance

  3. Hierarchical Inheritance

  4. Multiple Inheritance (via Interfaces in C#)

11. Constructors in C#

• Question: What are constructors and their types in C#?

• Answer: Constructors are special methods used to initialize objects. Types include:

  1. Default Constructor

  2. Parameterized Constructor

  3. Static Constructor

12. Difference Between Object and Reference

• Question: What is the difference between an object and a reference in C#?

• Answer:

  • Object: An instance of a class that has memory allocated.

  • Reference: A variable that holds the address of the object, not the object itself.