.NET Interview Questions and Answers

1. What is ASP?

Active Server Pages (ASP), also known as Classic ASP, is a Microsoft's server-side technology, which helps in creating dynamic and user-friendly Web pages. It uses different scripting languages to create dynamic Web pages, which can be run on any type of browser. The Web pages are built by using either VBScript or JavaScript and these Web pages have access to the same services as Windows application, including ADO (ActiveX Data Objects) for database access, SMTP (Simple Mail Transfer Protocol) for e-mail, and the entire COM (Component Object Model) structure used in the Windows environment. ASP is implemented through a dynamic-link library (asp.dll) that is called by the IIS server when a Web page is requested from the server.

2. What is ASP.NET?

ASP.NET is a specification developed by Microsoft to create dynamic Web applications, Web sites, and Web services. It is a part of .NET Framework. You can create ASP.NET applications in most of the .NET compatible languages, such as Visual Basic, C#, and J#. The ASP.NET compiles the Web pages and provides much better performance than scripting languages, such as VBScript. The Web Forms support to create powerful forms-based Web pages. You can use ASP.NET Web server controls to create interactive Web applications. With the help of Web server controls, you can easily create a Web application.

3. What is the basic difference between ASP and ASP.NET?

The basic difference between ASP and ASP.NET is that ASP is interpreted; whereas, ASP.NET is compiled. This implies that since ASP uses VBScript; therefore, when an ASP page is executed, it is interpreted. On the other hand, ASP.NET uses .NET languages, such as C# and VB.NET, which are compiled to Microsoft Intermediate Language (MSIL).

4. In which event are the controls fully loaded?

Page load event guarantees that all controls are fully loaded. Controls are also accessed in Page_Init events but you will see that view state is not fully loaded during this event

5. How can we identify that the Page is Post Back?

Page object has an "IsPostBack" property, which can be checked to know that is the page posted back.

6. What is the lifespan for items stored in ViewState?

The items stored in ViewState live until the lifetime of the current page expires including the postbacks to the same page.

7. How information about the user's locale can be accessed?

The information regarding a user's locale can be accessed by using the System.Web.UI.Page.Cultureproperty.

8. What is the difference between SQL notification and SQL invalidation?

The SQL cache notification generates notifications when the data of a database changes, on which your cache item depends. The SQL cache invalidation makes a cached item invalid when the data stored in a SQL server database changes.

9. Which is the parent class of the Web server control?

The System.Web.Ul.Control class is the parent class for all Web server controls.

10. Can you set which type of comparison you want to perform by the CompareValidator control?

Yes, by setting the Operator property of the CompareValidator control.

11. What is the behavior of a Web browser when it receives an invalid element?

The behavior of a Web browser when it receives an invalid element depends on the browser that you use to browse your application. Most of the browsers ignore the invalid element; whereas, some of them display the invalid elements on the page.

12. What are the advantages of the code-behind feature?

The code-behind feature of ASP.NET offers a number of advantages:

Makes code easy to understand and debug by separating application logic from HTML tags

Provides the isolation of effort between graphic designers and software engineers

Removes the problems of browser incompatibility by providing code files to exist on the Web server and supporting Web pages to be compiled on demand.

13. How do you sign out from forms authentication?

The FormsAuthentication.Signout() method is used to sign out from the forms authentication.

14. What is AutoPostBack?

If you want a control to postback automatically when an event is raised, you need to set the AutoPostBackproperty of the control to True.

15. What is the function of the ViewState property?

The ASP.NET 4.0 introduced a new property called ViewStateMode for the Control class. Now you can enable the view state to an individual control even if the view state for an ASP.NET page is disabled.

16. Why do you use the App_Code folder in ASP.NET?

The App_Code folder is automatically present in the project. It stores the files, such as classes, typed data set, text files, and reports. If this folder is not available in the application, you can add this folder. One of the important features of the App_Code folder is that only one dll is created for the complete folder, irrespective of how many files it contains.

17. Define a multilingual Web site.

A multilingual Web site serves content in a number of languages. It contains multiple copies for its content and other resources, such as date and time, in different languages.

18. What is an ASP.NET Web Form?

ASP.NET Web forms are designed to use controls and features that are almost as powerful as the ones used with Windows forms, and so they are called as Web forms. The Web form uses a server-side object model that allows you to create functional controls, which are executed on the server and are rendered as HTML on the client. The attribute, runat="server", associated with a server control indicates that the Web form must be processed on the server.

19. What is the difference between a default skin and a named skin?

The default skin is applied to all the Web server controls in a Web form, which are of similar type, and it does not provide a Skin ID attribute. The named skin provides a Skin ID attribute and users have to set the Skin ID property to apply it.

20. What is IIS? Why is it used?

Internet Information Services (IIS) is created by Microsoft to provide Internet-based services to ASP.NET Web applications. It makes your computer to work as a Web server and provides the functionality to develop and deploy Web applications on the server. IIS handles the request and response cycle on the Web server. It also offers the services of SMTP and FrontPage server extensions. The SMTP is used to send emails and use FrontPage server extensions to get the dynamic features of IIS, such as form handler.

21. What is Query String? What are its advantages and limitations?

The Query String helps in sending the page information to the server.

The Query String has the following advantages:

• Every browser works with Query Strings.
• It does not require server resources and so does not exert any kind of burden on the server.

The following are the limitations of Query String:

• Information must be within the limit because URL does not support many characters.
• Information is clearly visible to the user, which leads to security threats.

22. What is actually returned from server to the browser when a browser requests an .aspx file and the file is displayed?

When a browser requests an .aspx file then the server returns a response, which is rendered into a HTML string.

23. How can you display all validation messages in one control?

The ValidationSummary control displays all validation messages in one control.

24. Which two new properties are added in ASP.NET 4.0 Page class?

The two new properties added in the Page class are MetaKeyword and MetaDescription.

25. What is tracing? Where is it used?

Tracing displays the details about how the code was executed. It refers to collecting information about the application while it is running. Tracing information can help you to troubleshoot an application. It enables you to record information in various log files about the errors that might occur at run time. You can analyze these log files to find the cause of the errors.

In .NET, we have objects called Trace Listeners. A listener is an object that gets the trace output and stores it to different places, such as a window, a file on your locale drive, or a SQL Server.

The System.Diagnostics namespace contains the predefined interfaces, classes, and structures that are used for tracing. It supplies two classes, Trace and Debug, which allow you to write errors and logs related to the application execution. Trace listeners are objects that collect the output of tracing processes.

26. What is the difference between authentication and authorization?

Authentication verifies the identity of a user and authorization is a process where you can check whether or not the identity has access rights to the system. In other words, you can say that authentication is a procedure of getting some credentials from the users and verify the user's identity against those credentials. Authorization is a procedure of granting access of particular resources to an authenticated user. You should note that authentication always takes place before authorization.

27. How can you register a custom server control to a Web page?

You can register a custom server control to a Web page using the @Register directive.

28. Which ASP.NET objects encapsulate the state of the client and the browser?

The Session object encapsulates the state of the client and browser.

29. Differentiate globalization and localization.

The globalization is a technique to identify the specific part of a Web application that is different for different languages and make separate that portion from the core of the Web application. The localization is a procedure of configuring a Web application to be supported for a specific language or locale.

30. What is ViewState?

The ViewState is a feature used by ASP.NET Web page to store the value of a page and its controls just before posting the page. Once the page is posted, the first task by the page processing is to restore the ViewState to get the values of the controls.