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Top 17 Web API Interview Questions and Answers

30/Sep/2021 | 12 minutes to read

dotnet

Here is a List of essential Web API Interview Questions and Answers for Freshers and mid level of Experienced Professionals. All answers for these Web API questions are explained in a simple and easiest way. These basic, advanced and latest Web API questions will help you to clear your next Job interview.

Web API Interview Questions and Answers

These interview questions are targeted for ASP.NET Web API. You must know the answers of these ASP.NET Web API interview questions to clear a .NET developer interview.

1. What is the RESTful API?

Web service APIs that comply with REST principles are called RESTful APIs. You can define the RESTful APIs using:

  • A base URI - Unique resource identifier.
  • HTTP methods - GET, PUT, POST, PATCH, DELETE mapped with CRUD operations.
  • A media type for data - used to exchange the information using data formats such as JSON (JavaScript Object Notation) and XML.
For more visit RESTful APIs.

2. What are ASP.NET Web APIs?

ASP.NET Web APIs - A platform to build secure RESTful APIs which can be accessed by a broad range of clients including browsers, Daemon Apps, and mobiles devices. In ASP.NET, you can use the same framework to build web pages and services. For more visit ASP.NET Web APIs

3. How will you differentiate SOAP APIs from RESTful APIs?

REST APIs are lightweight as there is no built-in security and transaction compliance. Because of their lightweight REST APIs are good choices for mobile application development, IoT (Internet of Things) and serverless computing. SOAP APIs provide built-in security, error handling, and transaction compliance which makes them heavier as compared to REST APIs. And REST APIs are fast as no additional processing is required.
SOAP APIs work well in distributed environments whereas REST APIs are used for point-to-point communication. SOAP uses XML message format whereas REST APIs use JSON message format smaller than XML.
For more visit SOAP and REST API and SOAP vs REST.

4. What are the methods supported by ASP.NET Web API?

ASP.NET Web API offers four main HTTP methods which can be mapped to CRUD operations.

  • GET is used to retrieve the resource at specified URI.
  • PUT is used to update a resource at specified URI and can create a new resource if the server allows the client to specify a new URI.
  • POST is used to create new resources.
  • DELETE performs deletion of a resource at specified URI.
  • PATCH also used to update a resource by specifying a set of instructions - means how the resource should be modified.

5. Describe ASP.NET Core Web API.

Web API is a framework that is used to develop REST APIs that can be consumed by any client. ASP.NET Core provides the ability to develop RESTful services also known as Web APIs. Web API uses the concept of controllers derived from the ControllerBase class to handle the requests.

6. Differentiate MVC and Web API.

ASP.NET MVC is a framework to develop web apps and APIs using MVC architecture. When you are driving your API controller class from Controller base class then it adds the support for views but when you want to create Web APIs then derive your API controller class from ControllerBase class. So MVC is just a design pattern and ASP.NET Web API is a framework to build RESTful APIs.

5. Explain commonly used attributes in ASP.NET Web API.

Commonly used attributes are Route, Bind, HttpGet, Consumes, Produces etc. For more you can visit Attributes.

7. What behaviors does the ApiController attribute provide?

When you apply ApiController attribute on a controller class in a web API application, It allows you to take the benefit of below opinionated, API-specific behaviors.
  • Attribute based routing requirement
  • Model validation errors can automatically trigger HTTP 400 responses
  • Binding source parameter inference - which includes the attributes such as [FromBody], [FromForm], [FromHeader], [FromQuery], [FromRoute] and [FromServices].
  • Multipart/form-data request inference
  • Problem details for error status codes
For more visit ApiController Attribute.

8. How to disable automatic HTTP 400 responses in Web API?

You can disable the automatic trigger of HTTP 400 responses by setting SuppressModelStateInvalidFilter to 'True' in Startup.ConfigureServices as below. 


    services.AddControllers()
    .ConfigureApiBehaviorOptions(options =>
    {
    options.SuppressModelStateInvalidFilter = true;
    });

9. Explain the controller action return types that ASP.NET Core web API provides.

ASP.NET Core Web API offers the following return types for controller action methods.
  • A Specific Type - An action method can return any primitive data type like string or any custom object.
  • IActionResult type - It is used when you are expecting multiple ActionResult return types such as 'NotFoundResult', 'OkObjectResult', 'BadRequestResult' from an action method.
  • ActionResult<T>It allows you to return a type that derives from ActionResult type or some specific type like string.
For more visit Action return types in Web API.

10. How to handle JSON Patch requests in an ASP.NET Core web API?

11. How will you format response data in ASP.NET Core Web API?

For more visit https://learn.microsoft.com/en-us/aspnet/core/web-api/advanced/formatting?view=aspnetcore-8.0

12. Explain the custom formatters.

13. Explain error handling in ASP.NET Core web APIs?

14. How will you choose from a class library project or Web API?

15. What is OpenApi?

16. What is Swagger?

17. How will you generate web API documentation using Swagger/OpenAPI?

18. What is Rate Limiting? How will you implement it in the Web API?

18. What does JWT token contain? Explain about it.

For more about JWT Token visit JWT Introduction and JWT Token.

17. How to validate JWT token in .NET 5 APIs?

For more visit Create And Validate JWT Token In .NET 5.0.

Some General Interview Questions for Web API

1. How much will you rate yourself in Web API?

When you attend an interview, Interviewer may ask you to rate yourself in a specific Technology like Web API, So It's depend on your knowledge and work experience in Web API.

2. What challenges did you face while working on Web API?

This question may be specific to your technology and completely depends on your past work experience. So you need to just explain the challenges you faced related to Web API in your Project.

3. What was your role in the last Project related to Web API?

It's based on your role and responsibilities assigned to you and what functionality you implemented using Web API in your project. This question is generally asked in every interview.

4. How much experience do you have in Web API?

Here you can tell about your overall work experience on Web API.

5. Have you done any Web API Certification or Training?

It depends on the candidate whether you have done any Web API training or certification. Certifications or training are not essential but good to have.

Conclusion

We have covered some frequently asked Web API Interview Questions and Answers to help you for your Interview. All these Essential Web API Interview Questions are targeted for mid level of experienced Professionals and freshers.
While attending any Web API Interview if you face any difficulty to answer any question please write to us at info@qfles.com. Our IT Expert team will find the best answer and will update on the portal. In case we find any new Web API questions, we will update the same here.