Introducing ASP.NET Web API with Interview Questions Part-1
ASP.NET Web API is a framework designed to make it easy to build HTTP services that reach a broad range of clients, including browsers and mobile devices. It is an ideal platform for building RESTful applications on the .NET Framework. Here’s an introduction to the core concepts and components of ASP.NET Web API:
Key Features of ASP.NET Web API
HTTP Programming Model: ASP.NET Web API uses the full features of HTTP, such as request/response headers, URIs, and various HTTP methods (GET, POST, PUT, DELETE).
Content Negotiation: The framework supports content negotiation, where the server can respond to a client request in the format that the client can understand, such as JSON, XML, or any other media format.
Model Binding and Validation: ASP.NET Web API supports model binding and validation, similar to ASP.NET MVC, which simplifies the process of handling incoming data and validating it.
Routing: Web API uses routing to direct an HTTP request to a specific controller and action method. The framework uses attribute-based routing or convention-based routing to achieve this.
Dependency Injection: Dependency Injection (DI) is a design pattern used in software development to achieve Inversion of Control (IoC) between classes and their dependencies. Instead of a class creating its own dependencies, they are injected into the class, typically through its constructor, properties, or methods. This promotes loose coupling and enhances the testability, maintainability, and scalability of the application.
Filters: Filters in ASP.NET Web API allow you to execute custom logic before or after the action method runs. Common uses of filters include Authorization Filters, which handle authentication and authorization; Action Filters, which run code before and after action methods; Exception Filters, which handle unhandled exceptions; and Result Filters, which execute code before and after the action result is processed.
OData: ASP.NET Web API supports OData, a protocol that allows the creation and consumption of queryable and interoperable RESTful APIs in a simple and standard way.
Controller: A controller in Web API is a class that handles HTTP requests. It is derived from the ApiController class and contains action methods that correspond to HTTP verbs.
ASP.NET Web API Interview Type Questions
Q1. What is ASP.NET Web API?
ASP.NET Web API is a framework for building HTTP-based services that can be accessed from various clients, including browsers, mobile devices, and desktop applications. It is part of the ASP.NET platform and is used to create RESTful services, making it easier to build services that reach a broad range of clients, including web browsers and mobile devices.
Q2. What is the difference between ASP.NET Web API and WCF?
Purpose: ASP.NET Web API is designed specifically for creating RESTful services using HTTP, while WCF (Windows Communication Foundation) is a more comprehensive framework for building various types of networked services, including SOAP, REST, and more.
Protocol: Web API uses only HTTP, whereas WCF can use multiple protocols like TCP, HTTP, HTTPS, Named Pipes, and MSMQ.
Message Formats: Web API supports different media types like JSON, XML, etc., while WCF primarily uses SOAP (but can be configured to support other formats).
Configuration: Web API is configured via HTTP attributes and routing, making it simpler and more straightforward. WCF requires extensive configuration through XML-based configuration files.
Hosting: Web API can be hosted in IIS or self-hosted in an application. WCF can be hosted in IIS, Windows services, or self-hosted.
Q3. When to prefer ASP.NET Web API over WCF?
You should prefer ASP.NET Web API when:
You need to create a service that supports RESTful principles and can be consumed by various clients.
You need to build lightweight services that communicate using standard HTTP verbs (GET, POST, PUT, DELETE).
You want to easily support multiple media formats such as JSON, XML, etc.
You are looking for a simpler and more straightforward configuration and development model.
Q4. Which .NET Framework supports ASP.NET Web API?
ASP.NET Web API is supported in .NET Framework 4.0 and later. Additionally, it is available in .NET Core, making it cross-platform and allowing it to run on Windows, macOS, and Linux.
Q5. Can we consume ASP.NET Web API in applications created using other than .NET?
Yes, ASP.NET Web API can be consumed by applications created using any technology that can make HTTP requests. This includes JavaScript, Java, Python, PHP, Ruby, and mobile platforms like iOS and Android.
Q6. What is the difference between ASP.NET MVC application and ASP.NET Web API application?
Purpose: ASP.NET MVC is designed for building web applications that serve HTML to browsers. ASP.NET Web API is designed for building HTTP services that can be consumed by various clients.
Output: MVC actions typically return views (HTML content), while Web API actions return data (usually in JSON or XML format).
Routing: MVC uses attribute or convention-based routing geared towards web pages, whereas Web API uses attribute-based routing for handling RESTful URLs.
Protocol: MVC works primarily with the HTTP protocol, but it is more focused on rendering views. Web API is focused on HTTP services and uses HTTP methods directly for CRUD operations.
Q7. What are the RESTful Services?
RESTful services are web services that adhere to the principles of Representational State Transfer (REST). These services use standard HTTP methods (GET, POST, PUT, DELETE) to perform CRUD operations and are typically stateless. They return data in commonly used formats such as JSON or XML and are designed to be scalable and accessible from a wide range of clients.
Q8. What are the new features introduced in ASP.NET Web API 2.0?
ASP.NET Web API 2.0 introduced several new features, including:
Attribute routing: More control over the URIs in your web API.
CORS (Cross-Origin Resource Sharing): Allows you to make requests to your API from different domains.
OWIN (Open Web Interface for .NET) self-hosting: Host your Web API outside of IIS.
Improved dependency injection: Better support for DI frameworks.
Filter overrides: Ability to override filters applied globally or at the controller level.
IHttpActionResult: Simplifies unit testing and allows for more readable code.
Q9. Can we return View from Web API?
No, ASP.NET Web API is designed to return data, not views. If you need to return a view (HTML content), you should use ASP.NET MVC. Web API returns data in formats such as JSON, XML, or other media types, which is intended to be consumed by clients such as web browsers, mobile apps, etc.
Q10. Does ASP.NET Web API replace the WCF?
No, ASP.NET Web API does not replace WCF. They are intended for different purposes:
Use ASP.NET Web API for HTTP-based services and RESTful communication.
Use WCF for scenarios that require support for multiple protocols, service-oriented architecture (SOA), or advanced features like message queues, transactions, duplex communication, etc.
Q11. What is the difference between Under-Posting and Over-Posting in ASP.NET Web API?
Under-Posting: Occurs when a client sends insufficient data to the server, which may result in missing or incomplete data being processed. For example, when an object requires multiple fields but the client only sends a subset of those fields.
Over-Posting: Occurs when a client sends more data than required, potentially including sensitive or unintended data fields. This can lead to security risks such as accidental data exposure or updates to fields that should not be modified by the client.
Q12. What is Content Negotiation
Content Negotiation in ASP.NET Web API is a mechanism that allows the client and server to agree on the best format for the response data. It ensures that the server returns data in a format that the client can handle, such as JSON, XML, or any other media type. The process involves examining the Accept header in the HTTP request, which specifies the media types the client can process, and then the server selecting the most appropriate formatter to serialize the response data accordingly.