Top 25+ Dot NET Core Interview Questions and Answers

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.NET Core is a free open-source framework made by Microsoft. It came out in 2016 as a simpler and faster version of the old .NET Framework. The idea was led by Anders Hejlsberg, a well-known engineer at Microsoft. Dot NET Core works on Windows, Linux and macOS. That means developers can build many types of apps with it. Because it is so popular in real projects today, many companies ask Dot NET Core interview questions. Let’s look at the most common ones you should prepare.

Fun Fact: .NET Core is used by thousands of companies, including Microsoft, Stack Overflow, and Intel.

Basic Dot NET Core Interview Questions for Freshers

Here are some of the basic-level Dot NET Core interview questions and answers to help freshers get started.

1. What is .NET Core and how is it different from the .NET Framework?

.NET Core is a free, open-source framework from Microsoft used to build modern apps. It runs on Windows, Linux, and macOS. The .NET Framework, on the other hand, works only on Windows. .NET Core is faster, more flexible, and supports container-based deployments. It’s now part of the unified .NET 6/7/8 platform.

2. What are the main features of .NET Core?

.NET Core is cross-platform, modular, and fast. It supports CLI tools, cloud apps, microservices, and high-performance web APIs. It also offers built-in dependency injection, middleware, and modern language support like C# 12.

3. What is the use of the Startup.cs file in a .NET Core project?

The Startup.cs file is where you set up your app’s services and request pipeline. It has two main methods: ConfigureServices for adding services, and Configure for setting up middleware.

4. How does dependency injection work in .NET Core?

.NET Core has built-in support for dependency injection. You register services in ConfigureServices, then request them in controllers or classes through constructors. The framework takes care of creating and managing them.

5. What are middleware components in .NET Core?

Middleware are small pieces of code that handle requests and responses. They run in order and can modify requests, add headers, or stop the pipeline. Examples include routing, authentication, and logging middleware.

6. How do you handle configuration in a .NET Core application?

.NET Core reads configuration from multiple sources like appsettings.json, environment variables, and command-line arguments. You access these values using the IConfiguration interface.

7. What is Kestrel and why is it used in .NET Core?

Kestrel is a lightweight web server built into .NET Core. It is used to handle HTTP requests directly. It is fast, cross-platform, and works well with reverse proxies like Nginx or IIS.

Dot NET Core Interview Questions for Experienced

Here are the most common Dot NET Core interview questions designed for experienced professionals.

8. How do you manage versioning in a Web API built with .NET Core?

API versioning can be added using the Microsoft.AspNetCore.Mvc.Versioning package. You can version your APIs through URL segments, query strings, or custom headers. Each controller is tagged with [ApiVersion(“1.0”)] to route correctly.

9. What are the differences between IHostedService and BackgroundService in .NET Core?

IHostedService is the base interface for running background tasks. BackgroundService is an abstract class that simplifies long-running services using ExecuteAsync. Use IHostedService for full control, BackgroundService for simpler setups.

10. How does .NET Core handle garbage collection differently from the full .NET Framework?

.NET Core uses server and workstation garbage collectors, like the full framework. But it also supports low-latency modes and tiered compilation. These features improve memory use in high-performance apps.

11. How do you implement global exception handling in .NET Core?

Use UseExceptionHandler middleware in Startup.cs. You can also write custom middleware to catch exceptions and return formatted error responses. Logging can be added inside the exception pipeline.

12. What is the difference between AddSingleton, AddScoped, and AddTransient?

AddSingleton creates one instance for the app’s lifetime. AddScoped creates one per HTTP request. AddTransient creates a new instance every time it’s requested. Choosing the right one depends on the service usage.

13. How do you optimize performance in a high-load .NET Core application?

Use response caching, connection pooling, and async I/O. Minimize memory allocations and reuse objects when possible. You can also use a reverse proxy like Nginx and turn on HTTP/2 support for faster connections.

Dot NET Core Interview Questions for 5 Years Experienced

14. What challenges have you faced while migrating from .NET Framework to .NET Core?
15. How have you kept your .NET Core skills up to date in the last year?
16. Tell me about a time you had to debug a tough issue in production.
17. If your .NET Core API is slowing down under traffic, what steps would you take?
18. What is the role of the IApplicationBuilder and how do you use it?

Dot NET Core Interview Questions for 7 Years Experienced

19. What are the main architectural patterns you follow in .NET Core projects?
20. Which recent project in .NET Core are you most proud of, and why?
21. Describe a situation where you had to mentor a junior developer in .NET Core.
22. How would you handle authentication and authorization in a microservices setup using .NET Core?
23. How does .NET Core manage thread safety in asynchronous code?

Dot NET Core Interview Questions for 8 Years Experienced

24. How do you approach building scalable APIs in .NET Core?
25. What .NET Core features do you find most useful in enterprise applications?
26. Describe a time when you had to refactor a legacy .NET Core app.
27. What steps would you follow to debug memory leaks in a .NET Core app?
28. How does .NET Core handle dependency injection at runtime?

Dot NET Core Interview Questions for 10 Years Experienced

29. How has .NET Core evolved in your time working with it?
30. What architectural decisions have you made in large .NET Core projects?
31. Tell me about a time you managed a critical production outage involving a .NET Core service.
32. How would you structure a multi-tenant SaaS application using .NET Core?
33. What is your approach to logging and telemetry in enterprise-grade .NET Core apps?

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

Dot NET Core Advanced Interview Questions

These are advanced-level Dot NET Core interview questions to help you prepare for senior technical roles. 

34. How does the .NET Core runtime manage memory allocation and garbage collection?

The runtime uses generational garbage collection (Gen 0, Gen 1, Gen 2). It allocates memory in segments and reclaims unused objects automatically. Dot NET Core also supports low-latency and server GC modes for better control.

35. What is the difference between in-process and out-of-process hosting in .NET Core?

In-process hosting runs the app inside the IIS worker process (w3wp.exe), which improves speed. Out-of-process hosting runs the app using the Kestrel server and forwards requests from IIS or Nginx. In-process is faster and used by default.

36. How do you implement custom middleware, and what are some real use cases?

Custom middleware is written using a class with Invoke or InvokeAsync. You register it in Startup.cs using app.UseMiddleware<>(). Real examples include logging, response headers, request validation, or exception formatting.

37. What are span and memory types in .NET Core and when would you use them?

Span<T> and Memory<T> are used to handle slices of data without copying. Span works on the stack; Memory works on the heap and supports async use. They help with performance and low allocations.

38. How do you handle configuration in multi-environment deployments?

Use environment-specific files like appsettings.Development.json or appsettings.Production.json. Set the environment using ASPNETCORE_ENVIRONMENT. Dot NET Core loads the right settings based on that value at runtime.

Tips to Prepare for .NET Core Interview

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

• Review core concepts like middleware, dependency injection, and configuration.
• Practice explaining your recent projects clearly and confidently.
• Build a small sample project to refresh your skills.
• Revise the lifecycle of a .NET Core request pipeline.
• Know how to use IConfiguration and IServiceCollection.
• Brush up on C# features like async/await and LINQ.
• Use mock interviews or coding sites to practice under time pressure.

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

Wrapping Up

With these 25+ Dot NET Core interview questions and answers, you are better prepared to face any technical round with confidence. Keep practicing and stay updated with the latest features.

Looking for the right job? Go to Hirist – an online job portal for tech professionals. Here, you can easily find top .NET Core jobs in India.

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