Top 25 ASP.NET Interview Questions and Answers

1. What is ASP.NET?

Answer: ASP.NET is a web application framework developed by Microsoft. It allows developers to build dynamic web applications, websites, and web services. It is part of the .NET framework and supports multiple languages like C# and VB.NET.

2. What is the difference between ASP.NET WebForms and ASP.NET MVC?

Answer: ASP.NET WebForms is a traditional event-driven model for developing web applications, whereas ASP.NET MVC follows a Model-View-Controller architecture. MVC offers more control over HTML, provides better separation of concerns, and is more testable.

3. What is a Page Life Cycle in ASP.NET?

Answer: The page life cycle in ASP.NET includes the following stages:

• Page Request
• Start
• Initialization
• Load
• Postback
• Render
• Unload

4. What is the difference between a postback and a callback in ASP.NET?

Answer: A postback occurs when a page sends data to the server to reload and re-render the page. A callback is a partial page update, typically performed using AJAX, which sends data to the server without refreshing the entire page.

5. What are HTTP handlers and HTTP modules?

Answer: HTTP handlers are responsible for processing requests for specific resources (like images or custom data). HTTP modules are classes that can handle events during the HTTP request/response cycle and can be used for tasks like authentication, logging, and caching.

6. What is ViewState in ASP.NET?

Answer: ViewState is a mechanism in ASP.NET used to store the values of controls between postbacks. It helps maintain the state of the page and its controls during the page lifecycle.

7. What is a Master Page in ASP.NET?

Answer: A Master Page is used to provide a consistent layout and appearance across all pages of a web application. It allows developers to define a common template for pages, which can be shared across multiple content pages.

8. What is caching in ASP.NET?

Answer: Caching in ASP.NET is the process of storing frequently accessed data in memory to reduce the load on the server and improve performance. There are different types of caching, such as Output Caching, Data Caching, and Application Caching.

9. What is Web.config in ASP.NET?

Answer: Web.config is a configuration file used in ASP.NET applications to define settings for the application, such as database connections, security configurations, and custom error handling.

10. What are the different types of authentication in ASP.NET?

Answer: ASP.NET supports several types of authentication, including:

• Forms Authentication: Used for web-based applications to authenticate users with a login form.
• Windows Authentication: Used for intranet applications where users are authenticated using Windows credentials.
• Passport Authentication: Used to authenticate users with Microsoft's passport service.
• Custom Authentication: Allows developers to implement their own authentication mechanism.

11. What is Routing in ASP.NET MVC?

Answer: Routing in ASP.NET MVC is a mechanism that maps incoming HTTP requests to the appropriate controller and action method. It is based on URL patterns defined in the RouteConfig file.

12. What is the difference between a Controller and a View in ASP.NET MVC?

Answer: A Controller in ASP.NET MVC is responsible for handling user requests, interacting with the model, and selecting the appropriate view. A View is responsible for rendering the HTML output to the user.

13. What are Action Filters in ASP.NET MVC?

Answer: Action Filters are attributes that allow you to add extra functionality to controller actions. They can be used for tasks like logging, caching, or validation before or after the execution of an action method.

14. What is the purpose of the TempData collection in ASP.NET MVC?

Answer: TempData is used to pass data between controllers. Unlike ViewData and ViewBag, TempData persists data only for the duration of a single request. It is ideal for passing messages or data that needs to be available across redirects.

15. What is the difference between ViewData and ViewBag?

Answer: Both ViewData and ViewBag are used to pass data from controllers to views. ViewData is a dictionary object, while ViewBag is a dynamic object. ViewBag is more flexible and simpler to use because it doesn't require explicit type casting.

16. What is Dependency Injection in ASP.NET Core?

Answer: Dependency Injection (DI) is a design pattern used to achieve Inversion of Control (IoC). It allows for injecting dependencies into a class rather than hard-coding them, making the code more modular, testable, and maintainable. ASP.NET Core has built-in support for DI.

17. What is Entity Framework in ASP.NET?

Answer: Entity Framework (EF) is an Object-Relational Mapper (ORM) that allows developers to interact with a database using .NET objects, eliminating the need for writing SQL queries manually. EF supports both Code First and Database First approaches.

18. What is the difference between GET and POST methods in ASP.NET?

Answer: The GET method is used to request data from a server, and the data is sent in the URL. The POST method is used to send data to the server for processing, and the data is sent in the request body, making it more secure.

19. What is AJAX in ASP.NET?

Answer: AJAX (Asynchronous JavaScript and XML) is a technique used to update parts of a web page without reloading the entire page. In ASP.NET, it can be implemented using controls like UpdatePanel and client-side JavaScript.

20. What is the Global.asax file in ASP.NET?

Answer: Global.asax is an optional file used to define application-level events, such as Application_Start, Application_End, Session_Start, and Session_End. It is used to manage global application-level tasks like authentication, logging, and caching.

21. What is MVC 5 in ASP.NET?

Answer: MVC 5 is the latest version of ASP.NET MVC, which introduced new features like attribute routing, enhanced support for mobile devices, and improvements to the authentication and authorization system.

22. What is the use of IHttpHandler in ASP.NET?

Answer: IHttpHandler is an interface used to handle custom HTTP requests in ASP.NET. It allows developers to process incoming requests for resources like images, files, or custom data.

23. What are Bundling and Minification in ASP.NET?

Answer: Bundling is the process of combining multiple files (like CSS or JavaScript files) into a single file, while minification is the process of removing unnecessary characters (like spaces and comments) from those files to reduce their size and improve performance.

24. What are the benefits of using Web API over WCF?

Answer: Web API is simpler to use, more lightweight, and provides better support for RESTful services. It is better suited for modern web applications, while WCF is more suitable for SOAP-based communication.

25. What are the different types of sessions in ASP.NET?

Answer: ASP.NET provides several ways to store session data:

• In-Process Session: Stores session data in memory on the web server.
• State Server Session: Stores session data on a separate server.
• SQL Server Session: Stores session data in a SQL Server database.
• Custom Session: Allows you to define your own session storage mechanism.