C#.Net Advanced Level Interview Questions & Answers

1. What is ASP.NET?
   Answer: ASP.NET is a web application framework developed by Microsoft. It allows developers to build dynamic, data-driven web applications and services.
2. Explain the difference between ASP.NET Web Forms and ASP.NET MVC.
   Answer: ASP.NET Web Forms is a framework for building web applications using a drag-and-drop, event-driven model. ASP.NET MVC is a framework for building web applications using a model-view-controller architectural pattern.
3. What is the Page Life Cycle in ASP.NET?
   Answer: The Page Life Cycle is the sequence of events that occur when an ASP.NET page is processed, from initialization to rendering. It includes events like Page_Init, Page_Load, and Page_PreRender.
4. What is ViewState in ASP.NET?
   Answer: ViewState is a client-side state management technique used to store values between page postbacks. It preserves data on the page, allowing you to maintain the state of controls.
5. Explain the role of the Global.asax file in an ASP.NET application.
   Answer: The Global.asax file is used to define application-level events and application-wide settings. It contains event handlers like Application_Start, Application_End, and Session_Start.
6. What are ASP.NET Web Services?
   Answer: ASP.NET Web Services are components that allow you to build and expose web services using the SOAP protocol. They enable communication between different applications over the web.
7. What is an ASP.NET Web API?
   Answer: ASP.NET Web API is a framework for building HTTP services that can be consumed by a variety of clients, including web browsers and mobile devices. It uses standard HTTP methods for communication.
8. How do you handle errors in ASP.NET applications?
   Answer: Errors can be handled in ASP.NET using methods like try-catch blocks in code, custom error pages, and the global.asax file’s Application_Error event.
9. What is authentication and authorization in ASP.NET?
   Answer: Authentication verifies the identity of a user, while authorization determines the user’s access rights. ASP.NET provides various authentication and authorization mechanisms, including Forms Authentication and Windows Authentication.
10. Explain the purpose of the web.config file in ASP.NET.
    Answer: The web.config file contains configuration settings for an ASP.NET application. It specifies how the application behaves, including authentication, authorization, and custom error pages.
11. What are ASP.NET controls, and what are the two main categories?
    Answer: ASP.NET controls are server-side components that can be added to web forms. The two main categories are HTML controls and Web controls. HTML controls render as standard HTML elements, while Web controls offer additional functionality and are managed on the server.
12. What is the difference between “==” and “.Equals” in C#?
    Answer: “==” is used to compare the values of two objects, while “.Equals” is used to compare the content of objects. In C#, “==” is generally used for value types, while “.Equals” is often used for reference types.
13. How does Session State work in ASP.NET?
    Answer: Session State allows you to store and retrieve user-specific data across multiple requests. It uses a unique session ID for each user and can be configured to store data in-memory or in an external state server.
14. What is the purpose of the Response.Redirect method in ASP.NET?
    Answer: The Response.Redirect method is used to redirect a user’s browser to a different page. It sends an HTTP response with a status code of 302, causing the browser to request the new page.
15. How can you prevent Cross-Site Scripting (XSS) attacks in ASP.NET?
    Answer: To prevent XSS attacks, you should validate and sanitize user inputs, use the HttpUtility.HtmlEncode method to encode output, and implement input validation and request validation.
16. Explain the difference between “POST” and “GET” HTTP methods.
    Answer:
    “POST” is used to submit data to the server, typically for updating or creating resources.
    “GET” is used to retrieve data from the server, and the data is usually included in the URL.
17. What is the ASP.NET GridView control, and how is it used?
    Answer: The GridView control is used to display data in a tabular format. It can be bound to data sources like databases or collections and provides features for sorting, paging, and editing data.
18. How can you enable and configure debugging in an ASP.NET application?
    Answer: Debugging can be enabled by adding breakpoints in code and setting the “debug” attribute to “true” in the web.config file. You can use debugging tools like Visual Studio to step through the code.
19. Explain the purpose of the “using” statement in C#.
    Answer: The “using” statement is used for resource management, particularly for objects that implement the IDisposable interface. It ensures that resources are properly disposed of when they are no longer needed.
20. What is a PostBack in ASP.NET?
    Answer: A PostBack occurs when an HTML form is submitted to the server for processing. In the context of ASP.NET, it refers to the process of posting data back to the server for handling by server-side code.
21. Describe the concept of Master Pages in ASP.NET.
    Answer: Master Pages are templates that define the overall layout and structure of web pages in an application. Content pages can inherit from a Master Page, allowing for consistent design and layout.
22. How do you handle multiple forms on a single ASP.NET page?
    Answer: ASP.NET typically allows only one <form> element per page. To work with multiple forms, you can use JavaScript to handle form submission and data transmission asynchronously.
23. Explain the purpose of the Application_Start event in Global.asax.
    Answer: The Application_Start event is triggered when the application starts. It is used to perform one-time application initialization tasks, such as setting up application-wide variables or starting background processes.
24. What is Code-Behind in ASP.NET?
    Answer: Code-Behind is the practice of separating HTML markup (the .aspx file) from code logic (the .aspx.cs or .aspx.vb file). This separation enhances maintainability and promotes a clear distinction between design and functionality.
25. How can you cache data in ASP.NET to improve performance?
    Answer: You can cache data in ASP.NET using techniques like output caching, data caching, and fragment caching. Caching reduces the load on the server and improves page load times.
26. Explain the concept of ViewState in ASP.NET Web Forms.
    Answer: ViewState is used to store the state of controls on a page between postbacks. It ensures that control values are maintained across requests, providing a seamless user experience.
27. What is an ASP.NET Web User Control?
    Answer: An ASP.NET Web User Control is a reusable, self-contained component that can be added to web pages. It encapsulates both HTML and code and can be used across multiple pages. It promotes code reusability and modularity.
28. How do you handle session state management in ASP.NET?
    Answer: Session state management in ASP.NET is handled using the “Session” object. You can store and retrieve data in session variables to maintain user-specific information during a user’s session on the site.
29. What is the purpose of the “Globalization” and “Culture” settings in ASP.NET?
    Answer: Globalization and culture settings in ASP.NET allow you to adapt your application for different regions and languages. They affect how date and number formats, currency symbols, and text direction are displayed.
30. What are the different authentication modes available in ASP.NET?
    Answer: ASP.NET offers various authentication modes, including:
    – Forms Authentication: Allows custom login forms and user-specific authentication.
    – Windows Authentication: Uses Windows user accounts for authentication.
    – Passport Authentication: Integrates with Microsoft Passport services for single sign-on.
    – None: No authentication is required.

These basic-level interview questions and answers provide a foundation for discussing ASP.NET and its various aspects. During an interview, it’s essential to demonstrate a strong understanding of the basics, as they often serve as a starting point for deeper discussions about more advanced topics related to ASP.NET development.