Advance Web API Interview Questions | HTML KICK

Are you preparing for an interview for a Web API job? Here are some of the questions that you need to look at for you to be prepared mentally and have confidence. The article contains a couple of questions and the way they are supposed to be answered.

Advance Web API Interview Questions

What’s Web API?

This is a framework that assists one in building or developing an HTTP service.

What’s the importance of Web-API?

  • Web API is considered a service that offers us data or information from a server. It’s very significant because of the reasons below:
  • It’s used in accessing information from the database & save information back to the database.
  • It’s utilized in offering websites & client apps interfaces to access information.
  • Supports various text formats like JSON, and XML, etc.
  • Uses low-bandwidth like JSON or XML data, etc., & is then considered best for devices that have limited-bandwidth like smartphones, etc.
  • It’s compatible or suitable with any kind of browser & any kind of device like desktop, mobile, web, etc.
  • Web API is applicable for UI/UX. It improves interest in the company’s products & services and improves website traffic.

What’s Rest?

REST is a short form for Representational-State Transfer. This is an architectural pattern utilized for exchanging information in a distributed environment. With RESTt, there’s something known as Client & Server, & the data is exchanged between client & server over a distributed environment. Distributed-environment means a client can be at every platform like .NET, Java, PHP, etc. & the server will also be at every platform like .NET, Java, PHP, etc. REST architectural-pattern treats every service as a resource & a client could access the resources by utilizing HTTP Protocol ways like GET, PUT, POST, PATCH, & DELETE.

List the main return-types that are supported in Web-API?

It doesn’t have a specific data-type. This can return information of any kind depending on the business-requirement. There are numerous HTTP methods including GET, PUT, POST, etc., that return information in various formats depending on the use case.

What’s the advantage of using Rest at Web-API?

REST is more significant & beneficial in Web-API because of the following reasons:

  • It’s simple to use & lightweight.
  • It enables less information transfer between server & client.
  • It offers more flexibility.
  • It’s regarded best for utilizing it in mobile-apps because it makes less information transfer between server & client.
  • It handles & controls various kinds of calls, returning different data formats.
  • It utilizes simple HTTP-calls for inter-machine communication instead of using more complex choices like CORBA, SOAP, COM+, or RPC.

Which .NET-framework version supports Web-API?

NET version 4.0 & above is supported by web API.

Can one return-View from Web-API?

No, Web-API doesn’t return View though they reoccurrence the data. APIController helps in returning the information. So, if one needs to return a view from the controller class, then ensure to utilize or inherit the Controller class.

Web API utilizes which open-source library for JSON-serialization?

For JSON serialization Web API utilizes the Json.NET library

What’s SOAP?

This is an XML-message format utilized in web-service interactions. This enables one in sending messages over JMS or HTTP. Though other transport protocols are used. It’s also an XML-based messaging-protocol for exchanging data among computers.

What’s a Web-API filter?

A filter is used in adding extra logic at various levels of Web-API framework request-processing. Various kinds of Web-API filters include:

  • Authorization Filter: This filter handles authorization. It operates before controller-action. The filter is utilized in checking whether a client is authenticated or not. If the client isn’t authenticated, it returns HTTP status code-401 minus invoking the action.
  • Authentication Filter: This filter handles authentication & authenticates HTTP-requests. It also assists to authenticate client detail. It looks at the identity of a user.
  • Override Filter: It’s used for excluding specific action controllers or methods from controller level filter or global filter. It’s simply utilized in modifying the behavior of various filters for single-action methods.
  • AuthorizeAttribute: It’s an in-built authorization filter offered by Web-API.
  • Exception Filter: It’s used in handling exceptions that are unhandled in Web-API. It’s utilized every period the controller acts throw an exception which isn’t HttpResponseException. This implements an “IExceptionFilter” platform.
  • Action Filter: It’s attributing which one can apply to the entire controller or controller action. It’s used to add extra-logic after or before the controller action is executed. It’s just a way of adding extra functionality to Web-API services.

What are HTTP-Status Codes?

This is a 3-digit integer that the 1st digit of Status-Code states response class. The Response-Header of all API responses has HTTP Status-Code. HTTP Status-Codes are classified into 5 categories depending upon the 1st number.

What’s Media-Type Formatter concerning ASP.NET Web-API?

This is an abstract-class from that JsonMediaTypeFormatter which handles JSON-format & XmlMediaTypeFormatter which handles XML-format class gotten from. Media-Type-formatter is a class that’s responsible for serializing response information in the format which the client requested for.

What is Basic HTTP-Authentication?

This is a mechanism, where a user is approved through a service in which the client passes password and username in HTTP Authorization request-headers. Credentials are arranged as string “username:password”, based-encoded.

What’s the usage of Authorize-Attribute?

Web API offers an in-built authorization filter that includes Authorize Attribute. The filter checks if the user is valid or not. If it’s not, the user will view a 401-Unauthorized HTTP Status-Code.

How can one handle errors at Web API?

Web-API offers superb flexibility when it comes to error handling. Exception-handling is a method that’s utilized in handling run-time errors at application code. One will use HttpResponseException, Exception handlers, Exception filters, HttpError, register exception-filters to handle the errors. Moreover, the Exception filter also helps in identifying unhandled exceptions on controllers or actions, exception handlers are used in identifying any kind of unhandled-exception application-wide, & HttpResponseException is used when there’s a possibility of exception.

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Can one use Web-API with ASP.NET-Web Form?

Yes, one can use Web-API with ASP.Net-web form. As it’s bundled using ASP.NET-MVC framework. Moreover, it’s used with ASP.NET-Web Form.

What’s TestApi?

This is a utility-library of APIs. Using library tester-developer creates testing-tools & automated tests for .NET application utilizing data-structure & algorithms.

State exception filters?

It’s executed when the exceptions are unhandled & thrown from controller-method. The reason for the exception is everything. Exception filters implement the “IExceptionFilter” interface.

What’s Content Negotiation concerning Web API?

This is a process of choosing the best representation to a certain response from sets-of various numerous representations available. Next are 2 major headers which are responsible for Content Negotiation:

  • Accept: A different way for Content-Negotiation is to utilize Accept-Header. It’s utilized in specifying the format of information requested by the client from a server.
  • Content-Type: Content-type-header is utilized to specify server about data; the server will get from the client.

What’s Caching?

This is a method or process of keeping information somewhere or in cache for coming requests. A cache is a temporary-storage space. Caching keeps every recently or frequently accessed file or information in cache-memory & accesses them from the cache itself instead of the actual address of files or data. Cache interface just improves storage mechanism for response/request object pairs which are cached.

What are the types of Caching?

There are 3 kinds of caching as listed below:

  • Data Caching
  • Page Caching
  • Fragment Caching

What are the benefits of Caching?

  • It offers web-objects faster to end-user
  • It’s considered the best solution which guarantees that information is served where it’s required to be served that a high-level of efficiency that’s best for server and client
  • It makes the execution of every process faster
  • It decreases load-time on a website server
  • It reduces network costs

Can one pass numerous complex kinds in Web API?

Yes, one can pass numerous complex kinds in Web-API by using the following 2 methods:

Using Newtonsoft-array

Using ArrayList

What’s Web-API Versioning?

This is a method in which Web-API is decided to cope with business changes, & the API won’t impact client that’s using/consuming existing API. Numerous clients consume Web-API at a time, thus Web-API versioning is important & required as the business grows, & business requirement varies with time.

What’s CORS concerning Web API?

Cross-Origin Resource-Sharing (CORS) is a mechanism that enables one to create requests from a single website to a different website in a browser that’s normally not permitted by another policy known as Same Origin-Policy (SOP). This supports safe cross-origin requests & data transfers among browsers & servers or clients. The cross-origin request suggests requests coming from various origins. CORS resolves the same-origin constraint for JavaScript. One enables CORS for web-API using respective OWIN middleware or web-API package.

What’s the usage of DelegatingHandler?

DelegatingHandler is utilized to develop a custom-Server-Side HTTP-Message Handler at ASP.NET Web-API. Moreover, it’s utilized in representing Message-Handlers before routing to Web API.

Which parameters can be delivered in the API URL?

Documents keys, context keys, or anything which starts API to hit the exact end-point is few-parameters which one passes in URL to define the full end-point.

Which method validates every control on a page?


What’s the utilizing of DelegatingHandler?

DelegatingHandler is utilized to develop a custom-Server-Side HTTP-Message-Handler in ASP.NET Web-API. It’s utilized to represent-Message Handlers before one route in Web-API.

What are the new features which come with ASP.NET-Web API 2.0?

  • Attribute Routing
  • Cross-Origin Resource Sharing
  • Open Web-Interface NET
  • External Authentication
  • Web-API OData
  • HttpActionResult


Those are just samples of web API interview questions. There are a lot more others but you won’t miss a good number of these questions asked by the panel.

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