Web API – Top 25 Interview Questions and Answers for a Web API Technical Architect (.NET)

By familiarizing yourself with these top 25 Web API interview questions and their answers, you’ll be well-prepared to showcase your expertise, impress interviewers, and secure your position as a skilled architect in the ever-evolving world of .NET development.

What is Web API?

Web API is a framework that allows developers to build HTTP services that can be consumed by different clients. It is an ideal platform for creating RESTful APIs using .NET.

What is the difference between SOAP and REST?

SOAP (Simple Object Access Protocol) is a protocol for exchanging structured information in web services, whereas REST (Representational State Transfer) is an architectural style that uses HTTP for communication and is more lightweight and flexible.

How does Web API differ from WCF?

Web API is specifically designed for building HTTP services that follow RESTful principles, while WCF (Windows Communication Foundation) is a broader framework for building various types of services, including HTTP, TCP, and more.

Explain the HTTP methods commonly used in Web API.

 The most commonly used HTTP methods in Web API are GET (retrieve data), POST (create new data), PUT (update existing data), and DELETE (remove data).

What is the role of a routing table in Web API?

 A routing table maps incoming HTTP requests to specific actions or methods in Web API controllers based on the URL patterns defined in the routing configuration.

How can you enable CORS (Cross-Origin Resource Sharing) in Web API?

 CORS can be enabled in Web API by installing the Microsoft.AspNet.WebApi.Cors NuGet package and configuring it in the WebApiConfig file.

How can you secure Web API endpoints?

 Web API endpoints can be secured using various techniques such as OAuth, token-based authentication, API keys, or integrating with identity providers like Azure Active Directory.

What is content negotiation in Web API?

 Content negotiation in Web API allows clients to specify the desired response format (JSON, XML, etc.) using the Accept header, and the server responds with the requested format if available.

How can you handle errors in Web API?

 Errors in Web API can be handled using exception filters, global error handling using the ExceptionHandler attribute, or custom error handling logic within the application.

Explain the role of MediaTypeFormatter in Web API.

 MediaTypeFormatters in Web API are responsible for serializing and deserializing data between the server and clients. They handle formatting of data based on the requested content type.

How can you implement versioning in Web API?

 Web API versioning can be implemented using URL-based versioning, query parameter versioning, or through custom request headers.

What are filters in Web API?

 Filters in Web API allow developers to implement cross-cutting concerns such as authorization, exception handling, logging, and more. Filters can be applied globally or on specific controllers or actions.

How can you handle file uploads in Web API?

 File uploads in Web API can be handled by configuring the MultipartFormDataStreamProvider and using the MultipartFormDataContent class to send files from clients.

What are the advantages of using IHttpActionResult over HttpResponseMessage in Web API?

 IHttpActionResult provides a more concise and structured way to return HTTP responses from Web API actions. It simplifies the code and improves code maintainability.

Explain the role of DTO (Data Transfer Object) in Web API.

 DTOs are used to transfer data between the client and server in a structured format. They help decouple the internal data representation from the exposed API data structures.

How can you enable caching in Web API?

 Caching in Web API can be enabled by using the OutputCache attribute on controller actions or by implementing custom caching logic using MemoryCache or distributed caching mechanisms.

How does Web API handle model validation?

 Web API handles model validation using data annotations on model properties and validating incoming request data against those annotations. Invalid data triggers a validation error response.

Explain the role of dependency injection in Web API.

 Dependency injection in Web API allows for the inversion of control by providing loose coupling and better testability. It helps manage dependencies between different components of the application.

How can you implement pagination in Web API?

 Pagination in Web API can be achieved by using the Skip() and Take() methods on the data source or by leveraging libraries like Entity Framework for query paging.

What are the different return types in Web API?

 The different return types in Web API include void (no content), HttpResponseMessage (custom response), IHttpActionResult (structured response), or specific data types such as IQueryable, IEnumerable, or custom DTOs.

How can you enable SSL (HTTPS) in Web API?

 SSL can be enabled in Web API by obtaining and installing an SSL certificate on the server and configuring the application to require HTTPS in the hosting environment.

Explain the concept of content negotiation with attribute routing in Web API.

Content negotiation with attribute routing in Web API allows developers to define multiple actions in a controller with the same name but different HTTP method attributes. Web API automatically selects the appropriate action based on the HTTP method used in the request.

How can you implement request/response compression in Web API?

Request/response compression in Web API can be achieved by using libraries like GZip or Deflate, which compress the data sent between the server and the client to reduce network bandwidth.

What are the best practices for performance optimization in Web API?

Performance optimization in Web API can be achieved by implementing caching, minimizing database calls, using asynchronous programming, leveraging proper indexing, optimizing data serialization, and implementing appropriate resource management.

How does Web API handle concurrency and scalability?

Web API inherently supports concurrency and scalability through the use of HTTP and statelessness. It can be further enhanced by employing distributed caching, load balancing, and horizontal scaling techniques.