Introduction

Are you preparing for a .NET developer job and gearing up for a
technical interview? To help you succeed, we’ve compiled a comprehensive list
of the top 20 common
.NET Core interview questions for experienced developers. These
questions cover many topics, such as ASP.NET Core,
C#, concurrency, etc. Whether you’re an experienced developer or just starting
your career in .NET, these questions will help you prepare for your interview
and stand out. 

Introduction to .NET Core

1. What is ASP.NET Core, and why is it important?

ASP.NET Core is a modern, open-source framework for building cross-platform
web applications and APIs. It’s lightweight, modular, and designed for
Windows, Linux, and macOS.
ASP.NET Core
unifies MVC and Web API into a single model, making it flexible for web,
mobile backends, and IoT applications. Microsoft and a vibrant community back
it and offer strong tooling, extensive documentation, and a robust ecosystem.

2. How does ASP.NET Core differ from the traditional ASP.NET framework?

The primary differences between ASP.NET Core and traditional ASP.NET are-

• Platform– ASP.NET Core is cross-platform, while traditional ASP.NET
  is Windows-only.
• Size– ASP.NET Core is modular and lightweight, whereas traditional
  ASP.NET is larger and more complex.
• Performance– ASP.NET Core generally performs better due to its
  streamlined architecture.
• Configuration– ASP.NET Core uses flexible, code-based configuration
  instead of XML.
• Open Source– ASP.NET Core is fully open-source, while traditional
  ASP.NET is primarily closed-source.

Core Concepts

3. What is the role of the Startup class in ASP.NET Core?

The Startup class in ASP.NET Core is the central point for configuring your
application’s services and request pipeline. It contains two primary methods-
ConfigureServices, where you register services for dependency injection, and
Configure, where you define the middleware pipeline.

4. Explain Dependency Injection in ASP.NET Core.

Dependency Injection
(DI) is a design pattern used to manage dependencies in your code. ASP.NET
Core has a built-in DI container that handles the creation and lifetime of
services. This promotes loose coupling and enhances testability by allowing
you to inject services where needed rather than creating them directly.

Benefits and Features

5. What are the key benefits of using ASP.NET Core?

• Cross-platform– Develop applications for Windows, macOS, and Linux.
• Performance– Lightweight and fast with minimal resource usage.
• Unified APIs– A consistent approach to building web UIs and APIs.
• Modularity– Easily customizable and testable.
• Cloud Integration– Seamless integration with cloud platforms like
  Azure.
• Community-driven– Extensive resources and continuous improvement.

Request Handling

6. Describe the request processing pipeline in ASP.NET Core.

The ASP.NET Core request processing pipeline, or middleware pipeline, is a
modular component sequence that handles
HTTP
requests. Each middleware component performs specific tasks, such as
authentication, logging, or routing, and passes the request to the next
component in the sequence.

7. What is the difference between app.Run and app.Use in middleware
configuration?

• app.Run– Adds a terminal middleware that processes the request and
  ends the pipeline.
• app.Use– Adds a non-terminal middleware that processes the request
  and passes it to the next middleware.

Delegates and Hosting

8. What is a Request delegate in ASP.NET Core?

A Request delegate is a function that handles an HTTP request. It’s a core
part of the middleware pipeline, processing requests and generating responses.

9. Explain the role of the Host in ASP.NET Core.

The Host in ASP.NET Core manages the application’s lifecycle and resources. It
handles configuration, dependency injection, logging, and web server
integration, ensuring the application runs smoothly from startup to shutdown.

Configuration and Static Files

10. How does Configuration work in ASP.NET Core, and how do you read values
from the appsettings.json file?

Configuration in ASP.NET Core uses key-value pairs from various sources like
files (appsettings.json) and environment variables. You can access
configuration values using the IConfiguration interface, which is typically
injected into your classes. For example-

11. How does ASP.NET Core handle static file serving?

ASP.NET Core uses the UseStaticFiles middleware to serve static files like
images, HTML, and CSS. You configure this middleware to point to the static
file folder, usually wwwroot, to directly handle requests for these files.

State Management and Docker

12. Explain Session and State Management in ASP.NET Core.

Session and State Management in ASP.NET Core involve storing and maintaining
data across multiple user requests. This can be user-specific (like shopping
carts) or application-wide (like configuration settings). Sessions use cookies
for tracking, while other options include caching or databases for holding
global state.

13. Can ASP.NET Core applications run in Docker containers?

Yes, ASP.NET Core applications can run in Docker containers, which offer
portability, scalability, and simplified deployment. Docker containers are
lightweight and provide isolated environments ideal for microservices
architecture.

Model Binding and Validation

14. What is Model Binding in ASP.NET Core?

Model Binding in ASP.NET Core automatically maps data from HTTP requests (like
forms or JSON) to C# model objects in your controller actions. This simplifies
the development process by eliminating the need for manual data parsing.

15. How do you perform custom validation logic in ASP.NET Core? Custom
validation logic in ASP.NET Core can be implemented using-

• IValidatableObject– Implement the Validate method in your model to
  add custom validation rules.
• Custom Validation Attributes– Create custom attributes by inheriting
  from the ValidationAttribute class and overriding the IsValid method.
• Validation Libraries– Use libraries like FluentValidation for a more
  intuitive syntax and powerful validation capabilities.

MVC Architecture

16. Explain the ASP.NET Core MVC architecture.

ASP.NET Core MVC architecture follows the Model-View-Controller (MVC) pattern, which separates concerns in your application-

• Models– Represent data and business logic.
• Views– Handle the presentation layer.
• Controllers– Manage the interaction between models and views.

Components and ViewModels

17. Describe the components (Model, View, Controller) of ASP.NET Core MVC.

Models- Define the data and business rules.

Views- Render the user interface.

Controllers- Handle user requests, interact with models, and render views.

18. What is the purpose of ViewModels in ASP.NET Core MVC development?

ViewModels in ASP.NET Core MVC development act as a bridge between domain
models and views. They are custom classes designed to represent the data
required by a specific view, often combining information from multiple domain
models or adding display-specific logic.

Routing and Attributes

19. How does routing work in ASP.NET Core MVC applications?

Using route templates and middleware, routing in ASP.NET Core MVC directs
incoming URLs to the appropriate controller actions. When a match is found,
the corresponding action is invoked to handle the request.

20. What is Attribute-based routing in ASP.NET Core MVC?

Attribute-based routing allows you to define routes directly on controller
classes and action methods using Route attributes. This approach offers more
control and flexibility over the URIs your application exposes.

Conclusion

These 20 questions provide a solid foundation for preparing for a .NET Core
interview. By understanding these concepts and practising your answers, you’ll
be well-equipped to tackle any advanced
.NET Core interview questions
that come your way. Whether you’re an experienced developer or just starting,
mastering these topics will help you stand out in your next technical
interview.