ASP.NET Interview Questions

Top 50 most asked interview and answers with examples 

1. What is ASP.NET?

   - Answer: ASP.NET is a web development framework developed by Microsoft to build dynamic web applications and services.

2. Explain the Page Life Cycle in ASP.NET.

   - Answer: The ASP.NET page life cycle consists of events like Page_Init, Page_Load, Page_PreRender, and Page_Unload. For example, in the Page_Load event, you can initialize controls.

3. What is ViewState in ASP.NET?

   - Answer: ViewState is used to store state information between postbacks. For example, you can use ViewState to retain the value of a control across page requests.

4. Differentiate between ASP.NET Web Forms and ASP.NET MVC.

   - Answer: Web Forms follow a page-centric model, while MVC follows a controller-centric approach. For example, in Web Forms, controls have their events, while MVC relies on controllers to handle requests.

5. What is the ASP.NET authentication and authorization process?

   - Answer: Authentication verifies the identity of a user, while authorization determines the user's access level. For example, you can use Forms Authentication to authenticate users and define roles for authorization.

6. Explain the difference between Server.Transfer and Response.Redirect.

   - Answer: Server.Transfer transfers control from one page to another on the server, while Response.Redirect sends a redirect header to the browser. For example, Server.Transfer is faster as it happens on the server.

7. What is the Global.asax file used for in ASP.NET?

   - Answer: The Global.asax file contains application-level events like Application_Start and Session_Start. For example, you can use Application_Error to handle unhandled exceptions.

8. How can you secure your ASP.NET application?

   - Answer: You can use techniques like authentication, authorization, and encryption. For example, you can use SSL for secure communication and implement role-based authorization.

9. What are AJAX Extensions in ASP.NET?

   - Answer: AJAX Extensions enable asynchronous communication between the browser and server. For example, you can use UpdatePanel to update parts of a page without a full postback.

10. Explain the concept of caching in ASP.NET.

- Answer: Caching is used to store frequently accessed data to improve performance. For example, you can use Output Caching to cache the HTML output of a page.

11. What is the difference between ViewState and Session State in ASP.NET?

- Answer: ViewState is used to store state information for a single web page, while Session State is used to store information across multiple pages for a user session. For example, ViewState is suitable for retaining control values, while Session State can store user-specific data like login information.

12. Explain ASP.NET MVC Routing.

- Answer: Routing in ASP.NET MVC maps URLs to controller actions. For example, the route configuration specifies how URLs are parsed and which controller actions should handle them.

13. What is the role of the Globalization and Localization in ASP.NET?

- Answer: Globalization is the process of designing and developing applications that can adapt to different cultures, while Localization is the process of adapting the application to a specific culture. For example, using resource files to store strings in multiple languages facilitates localization.

14. Differentiate between TempData, ViewData, and ViewBag in ASP.NET MVC.

- Answer: TempData is used to pass data from the current request to the next request, ViewData is a dictionary to pass data from the controller to the view, and ViewBag is a dynamic wrapper around ViewData. For example, TempData is often used during redirects to maintain data.

15. What is the purpose of the Web.config file in ASP.NET?

- Answer: Web.config is a configuration file that stores settings for a web application. For example, it can contain database connection strings, custom error pages, and security settings.

16. Explain the use of the DataReader and DataSet in ADO.NET.

- Answer: DataReader is a read-only, forward-only cursor that provides high-performance access to data, while DataSet is an in-memory, disconnected representation of data. For example, DataReader is suitable for large datasets when you need to read data once, while DataSet is more appropriate when you need to work with data offline.

17. How does ASP.NET maintain session state?

- Answer: ASP.NET can maintain session state using in-process (default), SQL Server, or State Server mode. For example, using the InProc mode stores session data in the web server's memory.

18. What is the purpose of the App_Code folder in ASP.NET?

- Answer: The App_Code folder is used to store source code files that are automatically compiled at runtime. For example, you can place reusable classes or business logic files in this folder.

19. Explain the concept of Dependency Injection in ASP.NET.

- Answer: Dependency Injection is a design pattern where the dependencies of a class are injected from the outside. For example, using a dependency injection container to inject database or service dependencies into controllers.

20. What is the role of the ContentPlaceHolder in Master Pages in ASP.NET?

- Answer: ContentPlaceHolder is used in Master Pages to define regions where content pages can inject their content. For example, defining a ContentPlaceHolder for the main content area allows individual pages to customize their content within the overall page layout.

21. What is the difference between ASP.NET Core and ASP.NET Framework?

- Answer: ASP.NET Core is a cross-platform, high-performance framework, while ASP.NET Framework is Windows-only. For example, ASP.NET Core supports microservices architecture and can run on Linux, whereas ASP.NET Framework is primarily Windows-based.

22. Explain the role of the App_Start folder in ASP.NET.

- Answer: The App_Start folder contains startup code for the application, such as route configuration and filter registration. For example, WebApiConfig in App_Start is used to configure routes for Web API controllers.

23. What is the use of the @ symbol in Razor syntax?

- Answer: The @ symbol is used to switch from HTML to C# code in Razor syntax. For example,

@Model.PropertyName is used to display a

property value in a Razor view.

24. How does ASP.NET handle ViewState in Web Forms?

- Answer: ViewState is a hidden field on the page that stores state information. For example, you can disable ViewState for specific controls to reduce page size.

25. What is the purpose of the Global.asax file in ASP.NET?

- Answer: Global.asax contains application-level events like Application_Start and Application_End. For example, you can use Application_Error to handle unhandled exceptions globally.

26. Explain the role of the "using" statement in C#.

- Answer: The "using" statement is used for resource management, ensuring that objects like database connections or file streams are properly disposed of. For example, using (SqlConnection connection = new SqlConnection(connectionString)) { ... }.

27. What is Entity Framework in ASP.NET?

- Answer: Entity Framework is an Object-Relational Mapping (ORM) framework for database access. For example, it allows developers to interact with databases using C# classes instead of SQL.

28. How can you secure an ASP.NET application against SQL Injection attacks?

- Answer: Use parameterized queries or stored procedures to prevent SQL Injection. For example, instead of concatenating strings to form a query, use parameters.

29. Explain the concept of Bundling and Minification in ASP.NET.

- Answer: Bundling combines multiple CSS or JavaScript files into a single file, while minification reduces the size of these files. For example, bundling and minification improve page load times by reducing the number of requests and file sizes.

30. What is the role of the Web.config file in ASP.NET?

- Answer: Web.config is a configuration file that stores application settings, connection strings, and custom configurations. For example, you can define custom error pages or authentication settings in Web.config.

31. Explain the role of the ViewBag in ASP.NET MVC.

- Answer: ViewBag is a dynamic property that allows passing data from the controller to the view. For example, in the controller, you can use ViewBag.Message = "Hello, World!"; , and in the view, you can access it as @ViewBag.Message.

32. How can you handle errors in ASP.NET?

- Answer: Errors can be handled using custom error pages or by implementing theApplication_Errorevent in Global.asax. For example, redirecting to a custom error page when an exception occurs.

33. What is the purpose of the ModelState in ASP.NET MVC?

- Answer: ModelState is used to represent validation errors that occurred during model binding. For example, checking ModelState.IsValid

in the controller before processing form data.

34. Explain the concept of the ASP.NET Page Life Cycle.

- Answer: The Page Life Cycle defines the stages a web page goes through from initialization to rendering and unloading. For example, thePage_Load event is triggered during the loading stage.

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

- Answer: Action Filters are attributes that can be applied to controller actions to modify the behavior of an action method. For example, the [Authorize] attribute restricts access to an action to authenticated users.

36. How can you implement authentication in ASP.NET Core?

- Answer: Authentication in ASP.NET Core can be implemented using middleware, such as UseAuthentication in the startup configuration.  For example, configuring cookie authentication for user login.

37. What is the purpose of the async and await keywords in C#?

- Answer: The async and await keywords are used for asynchronous programming, allowing non-blocking execution of code. For example, async Task<ActionResult> MyAsyncMethod() in an ASP.NET MVC controller.

38. Explain the concept of Dependency Injection in ASP.NET Core.

- Answer: Dependency Injection is a technique where dependencies are injected into a class, promoting loose coupling. For example, registering and injecting services in the Startup.cs file.

39. What is the difference between TempData and Session in ASP.NET MVC?

- Answer: TempData is used to store data for a single HTTP request, while Session stores data across multiple requests. For example, TempData is useful for carrying data between redirects.

40. How can you implement CORS (Cross-Origin Resource Sharing) in ASP.NET Web API?

- Answer: CORS in ASP.NET Web API can be configured using the EnableCors attribute or by adding the appropriate headers in the response. For example, decorating a controller with [EnableCors(origins: "http://example.com",  headers: "*", methods: "*")].

41. Explain the concept of Areas in ASP.NET MVC.

- Answer: Areas are used to organize large ASP.NET MVC projects into smaller, more manageable sections. For example, creating an "Admin" area to separate admin-related controllers and views.

42. What is the purpose of the WebApiConfig class in ASP.NET Web API?

- Answer: WebApiConfig is used to configure routing for ASP.NET Web API. For example, defining routes to map HTTP requests to specific controller actions.

43. How can you implement caching in ASP.NET?

- Answer: Caching in ASP.NET can be implemented using the OutputCache directive or programmatically using HttpRuntime.Cache. For example, applying OutputCacheto cache the output of a controller action.

44. What is the role of the Global Filter in ASP.NET MVC?

- Answer: Global Filters are applied to all controller actions in an MVC application, providing a way to apply cross-cutting concerns. For example, creating a global filter for logging.

45. Explain the purpose of the TempDataDictionary.Peek method in ASP.NET MVC.

- Answer: TempDataDictionary.Peek

is used to check if a key exists in TempData without removing it. For example, using TempData.Peek("message") to check if a message exists before displaying it.

46. How does the ASP.NET pipeline handle HTTP requests?

- Answer: The ASP.NET pipeline processes HTTP requests through a series of modules and handlers. For example, middleware in ASP.NET Core is used to configure the request-handling pipeline.

47. What is the use of the ActionName attribute in ASP.NET MVC?

- Answer: ActionName is used to specify an alternate name for an action method in an MVC controller. For example, [ActionName("Details")]

can be used to map an action method with a different name.

48. Explain the role of the ApiController attribute in ASP.NET Web API.

- Answer: The ApiController attribute is used to indicate that a controller class should be treated as a Web API controller. For example, [ApiController]

is applied to a class that inherits from ControllerBase in ASP.NET Core.

49. What is the purpose of the Cross-Site Request Forgery (CSRF) token in ASP.NET?

- Answer: CSRF tokens are used to protect against Cross-Site Request Forgery attacks by validating that the request originates from a trusted source. For example, including a CSRF token in a form and validating it on the server.

50. How can you implement role-based authorization in ASP.NET MVC?

- Answer: Role-based authorization can be implemented by decorating controllers or actions with [Authorize(Roles = "Admin")] . For example,  restricting access to an admin panel based on user roles.