Top Interview Questions for .NET Core Web API Developers: Ace Your Next Interview

Introduction

: Are you preparing for a .NET Core Web API developer interview? To help you excel in your upcoming interview, we’ve compiled a list of top interview questions frequently asked by tech companies. By familiarizing yourself with these questions, you’ll gain a competitive edge and feel confident in showcasing your expertise in .NET Core Web API development. Whether you’re a seasoned professional or just starting your career, this comprehensive guide will equip you with the knowledge and insights needed to excel in your interview.

Top .NET Core Web API interview questions

1. What is .NET Core Web API and its key features?
   • Answer: .NET Core Web API is a framework for building HTTP-based web services using .NET Core. It allows developers to create RESTful APIs that can be consumed by various clients. Key features include cross-platform compatibility, lightweight and modular architecture, and support for dependency injection.
2. What are the main components of an ASP.NET Core Web API application?
   • Answer: An ASP.NET Core Web API application consists of controllers, models, and views. Controllers handle incoming requests and define actions to perform. Models represent the data structure and define the business logic. Views are not used in Web API applications since they focus on data rather than generating HTML responses.
3. How do you handle authentication and authorization in .NET Core Web API?
   • Answer: Authentication and authorization can be handled using various mechanisms in .NET Core Web API. You can implement token-based authentication using JWT (JSON Web Tokens) or use external authentication providers like OAuth or OpenID Connect. Authorization can be achieved by applying attributes like [Authorize] to controller actions or using policy-based authorization.
4. How do you handle validation and error handling in .NET Core Web API?
   • Answer: Validation can be performed using model validation attributes like [Required], [MaxLength], etc., or custom validation logic. Errors can be handled by returning appropriate HTTP status codes (e.g., 400 for bad requests) along with error details in the response body. Global error handling can be implemented using middleware or filters.
5. What is dependency injection in .NET Core? How is it used in Web API development?
   • Answer: Dependency injection is a design pattern that allows objects to receive their dependencies from an external source. In .NET Core, it is built into the framework and helps decouple components, improve testability, and promote modular design. In Web API development, dependencies can be injected into controllers, services, or other components using the built-in DI container.
6. How do you handle concurrency and data access in .NET Core Web API?
   • Answer: Concurrency can be managed using techniques like optimistic concurrency, which involves using timestamps or version numbers to track changes. Data access in .NET Core Web API can be achieved through various approaches, such as using an ORM like Entity Framework Core for database operations, or raw SQL queries for more complex scenarios.

Here are a few more important interview questions related to HTTP verbs and API implementation, along with code examples:

How do you implement different HTTP methods (GET, POST, PUT, DELETE) in a .NET Core Web API?

Answer: In a .NET Core Web API, you can define different HTTP methods using the [HttpGet], [HttpPost], [HttpPut], and [HttpDelete] attributes on your controller actions. Here’s an example:

[HttpGet]
public IActionResult Get()
{
    // Code to retrieve and return data
}

[HttpPost]
public IActionResult Post([FromBody] MyModel model)
{
    // Code to create a new resource using the provided model
}

[HttpPut("{id}")]
public IActionResult Put(int id, [FromBody] MyModel model)
{
    // Code to update an existing resource with the provided ID and model
}

[HttpDelete("{id}")]
public IActionResult Delete(int id)
{
    // Code to delete a resource with the provided ID
}

How do you handle routing and parameter binding in .NET Core Web API?

Answer: In .NET Core Web API, routing is handled by the routing middleware, which maps incoming requests to the appropriate controller and action based on the URL. Route parameters can be specified in the URL or through attributes. Here’s an example:

[Route("api/[controller]")]
[ApiController]
public class UsersController : ControllerBase
{
    [HttpGet("{id}")]
    public IActionResult GetById(int id)
    {
        // Code to retrieve user data based on the provided ID
    }

    [HttpGet("search")]
    public IActionResult Search(string keyword)
    {
        // Code to search for users based on the provided keyword
    }
}

How do you handle data validation in .NET Core Web API?

Answer: Data validation can be performed using model validation attributes or custom validation logic. Model validation attributes like [Required], [MaxLength], and [Range] can be applied to properties in your model classes to enforce validation rules. Here’s an example:

public class UserModel
{
    [Required]
    public string Name { get; set; }

    [EmailAddress]
    public string Email { get; set; }

    [Range(18, 99)]
    public int Age { get; set; }
}

[HttpPost]
public IActionResult Create([FromBody] UserModel model)
{
    if (!ModelState.IsValid)
    {
        // Invalid data, return a bad request response
        return BadRequest(ModelState);
    }

    // Code to create a new user using the provided model
}

Application Source Code @ LearnSmartCoding GitHub

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Conclusion:

Preparing for a .NET Core Web API developer interview requires a solid understanding of key concepts, best practices, and real-world applications. By mastering the interview questions covered in this guide, you’ll be well-prepared to showcase your expertise and secure that coveted job offer. Remember to practice your answers, provide clear and concise explanations, and demonstrate your problem-solving skills. Good luck with your interview preparation, and may you excel in your .NET Core Web API developer career!