Can You Answer These Top 20 Web API Interview Questions?

web api interview questions

Web API developers and programmers face a highly competitive job market. In addition to your experience, education, and training, you will need to be familiar with technical interview questions and answers. These job-specific questions provide a reliable indication of your skill set and the knowledge a hiring manager may want to see in a potential candidate. Check if you can answer these top 20 Web API interview questions.

Top 20 Web API Interview Questions

1. What is Web API?

Web API is a framework that aids in the building and development of full features of HTTP services.

2. Who can use Web API?

Web API can be used by any client that supports HTTP verbs such as GET, PUT, POST, and DELETE. One significant advantage of Web API is that its services do not need any configuration. Therefore, clients can easily make use of Web API and even include its use in mobile devices.

3. Explain what REST and RESTFUL are.

REST stands for REpresentational State Transfer. It is a new architectural style of writing and developing a web app and is generally preferred over SOAP (Simple Object Access Protocol) technology because it leverages less bandwidth and is useful in cloud applications.

RESTFUL is a type of web service that is based on REST technology.  RESTFUL API uses HTTP coding for much of its functionality and centers on system resources as well as how the state of the resource should be conveyed over HTTP protocol.

4. What is the advantage of using REST in Web API?

REST makes fewer data transfers between client and server, which makes it advantageous for use in mobile apps. Moreover, REST also requires less configuration, especially when compared to WCF. Additionally, REST is easy to access, stateless (making it less compex and easy to cache), and extremely scalable.

5. What are the main return types supported in Web API?

The Web API controller action can return a variety of values. For example, “Void” means that it has returned empty content. “IHttpActionResult” internally calls ExecuteAsync to produce an HttpResponseMessage. “HttpResponseMessage” will convert the response to an HTTP message. Additionally, there are other types of values that you can write the serialized return value into the response body.


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6. Which .NET framework supports Web API?

NET version 4.0 and above support web API.

7. Is it feasible to use Web API with ASP.NET Web Form?

Yes, you can use Web API with ASP.Net Web Form. ASP.NET Web API is typically bundled with the ASP.NET MVC framework. However, it can be used with ASP.NET Web Form by adding Web API to the traditional ASP.NET Web Forms application.

You can do this in two basic steps. First, you will need to add a Web API controller that derives from the ApiController class and then add a route table to the Application_Start method.

8. What are the advantages of using ASP.NET Web API?

ASP.NET Web API is beneficial because it works with standard HTTP verbs such as GET, PUT, POST, and DELETE, for all CRUD operations. There is also comprehensive support for routing, and the MediaTypeFormatter generates responses are in JSON or XML format. Additionally, ASP.NET Web API can be hosted in IIS in addition to self-host outside of IIS. Finally, there is support for model binding and validation as well as OData.

9. State the differences between MVC and Web API.

Applications that have a User Interface use the MVC framework. As a result, MVC Web applications replies as both data and views. On the other hand, Web API is used for developing HTTP services that reply only as data.

MVC functions to create a web app, upon which we can build web pages. Additionally, the MVC returns the data in the JSON format by using JSONResult from the action method. Web API uses HTTP verbs. It returns XML or JSON to client.

Another significant difference is that Web API helps with the creation of RESTFUL services over the .Net framework, which the MVC framework does not support.

10. What is SOAP?

SOAP stands for Simple Object Access Protocol. It is an XML message protocol that facilitates web service interactions via the Internet between two programs. SOAP enables messages sent over HTTP or JMS, as well as alternative transport protocols. This XML-based messaging protocol for transmitting information between computers, even if the programs on the computers run on different platforms or use different programming languages.

11. List out the differences between WCF and Web API?

WCF is a framework for building and developing service-oriented applications, which can be consumed by clients that understand Extensible Markup Language or XML. WCF also supports protocols, such as HTTP, TCP, and Named Pipes. On the other hand, Web API is a different framework that focuses on HTTP services. It is an open source platform that supports most of the MVC features.

12. What is the benefit of Web API over WCF?

WCF services use the SOAP protocol, while Web API’s HTTP services do not. As a result, Web API services are more lightweight and are not bogged down with the addition of SOAP, which uses standard XML schema over HTTP that may possibly lead to slower performance.

While both Web API and WCF can be self-hosted or hosted in IIS, WCF is best for duplex communication and end-to-end message security. Web API can be used to create complete REST services. Web API doesn’t require any data contracts nor demand the same level of configuration as WCF.

13. What are exception filters?

Exception filters are executed when a controller action method throws the unhandled exception. Additionally, exception filters implement the “IExceptionFilter” interface. It is important to note that exception filters do not catch HttpResponseException exceptions because these exceptions are specifically designed to return the HTTP response.

14. How do you register exception filters?

There are multiple ways to register exception filters, although there are three main ways that most developers prefer. You can either decorate the action with the exception filter, decorate the controller with the exception filter or register the exception filter globally.

15. How can you address errors in Web API?

There are several classes available to handle errors in Web API. They include registering exception filters, exception filters, HttpError, and HttpResponseException.

16. How do you pass multiple complex types in Web API?

You can use the ArrayList or the Newtonsoft array to pass the complex types in Web API.

17. What testing tools are available for developing or testing Web API?

A few testing tools for REST API web services include Restlet, Axis, CFx, and Jersey API.

18. What open-source library does Web API use for JSON serialization?

Web API employs the JSON.NET library for JSON serialization.

19. What is a disadvantage of “Other Return Types” in Web API?

With “Other Return Types,” you cannot directly return an error code like the 404 error.

20. What is Web API Routing?

Web API Routing is comparable to ASP.NET MVC Routing. Web API supports convention-based routing and attribute routing. The purpose is to route an incoming HTTP request to a specific action method on a Web API controller.

Other Considerations for Web API Interview

Different Types of Questions

The 20 questions in this list were carefully curated to represent the top Web API interview questions you will likely see. However, do not neglect to practice the other types of questions about your work history and projects you have previously worked on. Additionally, before the interviewer goes deeper into web developer topics, he or she may also ask you a series of behavioral interview questions to see if you work well on a team and fit the company’s culture.

Exercises and Technical Coding Tests

Your interviewer may design quick exercises to gauge your skills. Alternatively, a potential employer may require a full technical coding exam that assesses the technical competency of the candidate. As a result, do not schedule anything for after the interview, in case the hiring manager would like to see an example of your skills right then and there during the meeting.

An interview in the Web API development and programming industry will likely take longer than other job interviews because of the technical considerations. For a more comprehensive Web API programming exam, your potential employer may instead request to schedule you to visit another time.

In either case, you should prepare to answer Web API programming questions. For instance, an interview may ask you to construct an HtmlResponseMessage, assign an alias name for ASP.NET Web API Action or even write an example of Web API Routing.

Preparing for Web API Interview Questions

A few mistakes when answering Web API interview questions include a lack of confidence or robotic responses that sound like a student regurgitating a definition from a textbook. It is critical that your responses sound natural and knowledgeable, giving the impression that you are familiar with the field and demonstrate a reasonable mastery in programming.

Consider a service like Interview School that allows you to rehearse your answers to authentic interview questions from real interviews around the world. Our AI technology will provide feedback on your response and evaluate your confidence, tone, and even response duration.

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Prepare your answers thoroughly. Rehearse them to sound natural and confident. Brush up on your programming skills and practice a few exercises. Ace your next Web API interview.


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Author: Kimberly Ellis
Kimberly is a researcher, content generator, and language lover. With over 15 years in the professional workplace, a Bachelors in Education, and a passion for accuracy, Kimberly is uniquely qualified to help others overcome the many struggles that come when pursuing new employment. Her mantra is, "May your coffee be strong, your lashes be long, and your Monday’s be short."