Top 30+ .NET Core Interview Questions and Answers

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Learning .NET Core has become essential for many tech roles today. It is the framework behind a lot of modern apps – from websites to cloud services. Companies want developers who understand how it works and how to build real projects with it. That’s why .NET Core questions are common in interviews for backend, full-stack, and API development jobs. In this blog, you will find 30+ .NET Core interview questions with clear answers – perfect for brushing up before your next round.

Fun Fact – Around 25% of software developers worldwide use the modern .NET 5+ framework.

Most Asked .NET Core Interview Questions

Here are some of the most commonly asked .NET Core interview questions and answers to help you prepare.

1. What is dependency injection in .NET Core and how does it work?

Dependency injection (DI) is a built-in feature in .NET Core. It allows you to pass required services to a class instead of creating them inside the class. You register services in ConfigureServices() using methods like AddSingleton, AddScoped, or AddTransient. Then, .NET Core injects those services wherever needed, typically through constructors.

2. How does the .NET Core request pipeline function?

The request pipeline is a sequence of middleware that handles HTTP requests. Each middleware can process, pass on, or stop a request. It is defined in the Configure method of Startup.cs. Order matters – authentication should come before routing, for example.

3. What are the main differences between .NET Framework and .NET Core?

.NET Core is cross-platform, open-source, and optimized for performance. The .NET Framework works only on Windows and is no longer actively developed. .NET Core supports cloud apps, microservices, and modern tooling like CLI.

4. What is the role of the Startup.cs file?

Startup.cs configures how the app behaves. It has two main methods: ConfigureServices() registers services for DI, and Configure() defines the middleware pipeline.

5. How is middleware used in a .NET Core application?

Middleware are components that inspect and act on HTTP requests and responses. You add them in the Configure() method using methods like app.UseRouting() or app.UseAuthentication(). They run in the order they are added.

6. What is Kestrel and when should it be used?

Kestrel is the default cross-platform web server in .NET Core. It is lightweight and fast. In production, it is often used behind a reverse proxy like Nginx or IIS, but it can also serve requests directly.

7. How does routing work in ASP.NET Core?

Routing maps URLs to actions. In older versions, it used conventional or attribute routing. In .NET Core 3.0+, endpoint routing is common. It uses UseRouting() and UseEndpoints() in Startup.cs to define route patterns and endpoints.

8. What are the lifetimes of services in dependency injection?

• Singleton: One instance for the entire app.
• Scoped: One instance per request.
• Transient: A new instance every time it’s requested.

Choose based on how long the object should stay alive.

9. What is the difference between IHostedService and BackgroundService?

IHostedService is the basic interface for background tasks. You implement StartAsync() and StopAsync(). BackgroundService is an abstract class that simplifies this process by letting you use ExecuteAsync() directly.

10. How do you handle configuration in different environments?

Use different appsettings.{Environment}.json files like appsettings.Development.json. Then, set the environment variable ASPNETCORE_ENVIRONMENT. The configuration system automatically loads the correct file at runtime.

.NET Core Interview Questions for Freshers

These are beginner-friendly .NET Core interview questions to help freshers build a strong foundation.

11. What is .NET Core and why is it popular?

.NET Core is a cross-platform framework by Microsoft. It is fast, open-source, and works on Windows, Linux, and macOS. It is popular because it is lightweight, modular, and ideal for modern cloud and web apps.

12. What are the basic components of a .NET Core application?

A .NET Core app typically includes Program.cs, Startup.cs, controllers, models, views (if using MVC), configuration files like appsettings.json, and middleware that shape the request pipeline.

13. What is the difference between .NET Core and ASP.NET Core?

.NET Core is the runtime framework. ASP.NET Core is built on top of it and is used for building web apps and APIs. ASP.NET Core uses features from .NET Core like cross-platform support and performance improvements.

14. How do you create a simple web API using .NET Core?

You can use Visual Studio or the .NET CLI to create a Web API project using the template command: dotnet new webapi to scaffold a basic API project. Then define your controller and routes. The framework handles the rest.

15. What is the purpose of appsettings.json?

appsettings.json holds configuration values like connection strings, API keys, or environment-specific settings. It is easy to read and can be overridden with environment-specific versions.

16. How do you inject a service in a controller?

First, register the service in Startup.cs or Program.cs using AddScoped or similar. Then, use constructor injection in your controller to receive the service.

17. What is Model-View-Controller (MVC) in ASP.NET Core?

MVC is a design pattern. The model handles data, the view displays the UI, and the controller manages logic and user input. ASP.NET Core MVC uses this to separate concerns and keep code organized.

18. What is the use of the Program.cs file in .NET Core?

Program.cs is the entry point of the app. It creates and runs the web host. In .NET 6 and above, it uses minimal hosting APIs to set up services, middleware, and configuration in a cleaner way.

.NET Core Interview Questions for Experienced Professionals

Let’s go through some important .NET Core interview questions and answers for experienced professionals.

19. How do you implement global exception handling?

Use the UseExceptionHandler middleware in Program.cs to catch unhandled exceptions. Inside it, return custom error responses or redirect to an error page. You can also log exceptions using built-in logging providers.

20. What is the best way to manage secrets in production?

Avoid hardcoding secrets in config files. Use services like Azure Key Vault or AWS Secrets Manager. For local development, use dotnet user-secrets. It stores secrets outside of source control.

21. How do you optimize performance for high-load APIs?

Use response caching and asynchronous calls. Minimize memory usage with Span<T> or pooling. Enable HTTP/2, compress responses, and use a reverse proxy like Nginx for better throughput.

22. How do you implement logging in a real-time system?

Use ILogger<T> for structured logging. Send logs to external systems like Seq or ELK. In high-speed scenarios, use non-blocking background logging with channels or queuing.

23. How do you set up API versioning in .NET Core?

Add the Microsoft.AspNetCore.Mvc.Versioning package. Then, use attributes like [ApiVersion(“1.0”)] on controllers. You can version APIs via query strings, headers, or URL paths.

24. What is the use of IHttpClientFactory?

It helps manage HttpClient instances. It avoids socket exhaustion by pooling connections and supports typed clients, named clients, and policies like retries or timeouts using Polly.

.NET Core Interview Questions for 2 Years Experienced

• How did you contribute to a .NET Core project in your last role?
• What is the difference between AddSingleton and AddScoped?
• How would you troubleshoot a failing dependency injection?
• Tell me about a time you worked under tight deadlines using .NET Core.
• How do you return custom error responses from an API?

.NET Core Interview Questions for 3 Years Experienced

• What was your most challenging project using .NET Core?
• How does the Configuration API work in .NET Core?
• How would you migrate a .NET Framework project to .NET Core?
• Describe a time when you helped improve application performance.
• How do you create and use custom middleware?

.NET Core Interview Questions for 5 Years Experienced

• How have your responsibilities changed over the years in .NET Core projects?
• What is the role of filters in ASP.NET Core?
• How would you handle caching in a large-scale API?
• Share a situation where you mentored a junior developer.
• How do you use AutoMapper in .NET Core?

.NET Core Interview Questions for 7 Years Experienced

• Describe a complex system you have built using .NET Core.
• What’s the difference between synchronous and asynchronous controllers?
• How would you implement health checks in a microservices environment?
• Tell me about a conflict during a .NET Core project and how you resolved it.
• How do you use Policy-based Authorization?

.NET Core Interview Questions for 8 Years Experienced

• What long-term architectural decisions have you made in past projects?
• What is a Hosted Service and when would you use it?
• How would you set up multitenancy in a SaaS app?
• How do you prioritize features during tight development cycles?
• What is the role of IOptions<T> and how do you use it?

.NET Core Interview Questions for 9 Years Experienced

• How do you stay current with .NET Core and related technologies?
• How does .NET Core handle garbage collection?
• How would you manage logging and tracing across distributed services?
• Talk about a decision you made that significantly improved system performance.
• How do you write unit tests for middleware?

.NET Core Interview Questions for 10 Years Experienced

• How has your development approach evolved over the years?
• How do you design a scalable API architecture?
• What would you do if a live service built with .NET Core starts timing out?
• Describe a time when you had to refactor legacy code at scale.
• How do you implement distributed caching in .NET Core?

Note – .NET Core interview questions and answers for 10 years experienced often include system design, architecture decisions, and real-world problem-solving scenarios.

.NET Core Advanced Interview Questions

Here are advanced .NET Core interview questions that test deep technical knowledge and real-world project experience.

25. What are Span<T> and Memory<T> and when would you use them?

Span<T> is a lightweight ref struct for working with memory slices. It’s stack-only and not usable across async calls. Memory<T> works similarly but can live on the heap, so it is safe with async code. Use them when performance matters, especially for parsing or processing large data buffers.

26. How do you handle async streaming in .NET Core?

Use IAsyncEnumerable<T> for async streaming. It allows sending data chunk by chunk without blocking the thread. Combine it with await foreach in consumers and return it from controllers when working with large datasets or real-time feeds.

27. What are minimal APIs and when should they be used?

Minimal APIs were introduced in .NET 6. They simplify API creation using fewer files and lines of code. There is no need for controllers or attributes. Use them for lightweight services, microservices, or quick prototypes where full MVC isn’t needed.

28. How does gRPC compare to REST in .NET Core?

gRPC is faster and uses HTTP/2 with binary protocol (protobuf). REST uses HTTP/1.1 with JSON. gRPC supports streaming and strict contracts, but is harder to test in browsers. Use REST for web-facing APIs; gRPC fits best for internal microservices.

29. What is the difference between in-process and out-of-process hosting?

In-process runs the app inside the IIS worker process (w3wp.exe), which offers better performance. Out-of-process uses Kestrel to handle requests and forwards them from IIS or Nginx. In-process is now the default for IIS hosting.

30. How does the Generic Host differ from the Web Host?

WebHost is only for web apps. GenericHost supports both web and non-web workloads like background services or console apps. It provides a unified hosting model and is the standard in .NET Core 3.0+ and .NET 6/7/8/9.

Also Read - Top 20+ Microservices Architecture Interview Questions and Answers

Other Important .NET Core Interview Questions

Now, let’s look at some additional .NET Core interview questions that are often asked across different roles.

.NET Core Interview Questions for Senior Developer

1. How do you structure a multi-project solution in .NET Core?
2. What logging strategies have you used in production?
3. How do you handle environment-based deployments?
4. How do you manage breaking changes in APIs?
5. How do you use feature toggles in large-scale systems?

.NET Core Interview Questions C# Corner

1. How do you use async/await in .NET Core APIs?
2. What is the purpose of the ConfigureServices method?
3. How is routing different in endpoint routing?
4. What is the difference between ActionResult and IActionResult?
5. How do you bind complex objects in controller actions?

Also Read - Top 30+ C# Interview Questions and Answers

.NET Core MVC Interview Questions

1. How is routing configured in .NET Core MVC?
2. What are ViewComponents and how are they used?
3. What is the difference between TempData and ViewData?
4. How does model binding work in MVC?
5. What are Tag Helpers in ASP.NET Core MVC?

.NET Core 6 Interview Questions

Here are some of the most asked .NET Core 6.0 interview questions based on real-world use and new features.

1. What is new in .NET 6 compared to .NET 5?
2. What are minimal APIs in .NET 6?
3. How do you use top-level statements in .NET 6?
4. What is the role of WebApplication.CreateBuilder?
5. How does Hot Reload work in .NET 6?

.NET Core Middleware Interview Questions

1. How do you create custom middleware?
2. What is the execution order of middleware?
3. How do you short-circuit the pipeline?
4. What is the purpose of UseRouting and UseEndpoints?
5. How can you log requests and responses using middleware?

.NET Core Life Cycle Interview Questions

1. What happens during application startup in .NET Core?
2. What is the difference between Configure and ConfigureServices?
3. How does the application process a request?
4. What is the role of the Program.cs file?
5. What is the difference between Build and Run in the app lifecycle?

How to Prepare for Your .NET Core Interview?

Here are some simple tips to help you prepare confidently for your .NET Core interview –

• Review core concepts like middleware, DI, and the request pipeline.
• Build a sample project using Web API or MVC.
• Practice explaining your recent work experience clearly.
• Revise async/await, routing, and service lifetimes.
• Go through actual error-handling and logging setups.
• Use mock interview platforms for timed practice.
• Stay updated with the latest .NET features (like .NET 9).
• Practice commonly asked .NET Core interview questions. 

Wrapping Up

With these 30+ .NET Core interview questions and answers, you will feel more confident during interviews. Keep practicing, stay updated, and focus on real project experience.

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