Top ASP.NET Interview Questions (2023)

public class MyAppDomain: MarshalByRefObject  
{  
    public string GetInfo()  
    {  
        return AppDomain.CurrentDomain.FriendlyName;  
    }  
}  
public class MyApp  
{  
    public static void Main()  
    {  
        AppDomain apd = AppDomain.CreateDomain("Rajendrs Domain");  
        MyAppDomain apdinfo = (MyAppDomain) apd.CreateInstanceAndUnwrap(Assembly.GetCallingAssembly( 
    )  
            .GetName()  
            .Name, "MyAppDomain");  
        Console.WriteLine("Application Name = " + apdinfo.GetInfo());  
    }  
} 

Request.QueryString(variable)[(index).count]

</asp:ContentPlaceHolder>  
   <br /> Footer...  
</form>

<authentication mode="Windows"/> 

<authorization>  
   <deny users="?"/>  
</authorization> 

<authentication mode="Windows">  
   <forms name=" AuthenticationDemo" loginUrl="logon.aspx" protection="All" path="/"timeout="30" />
</authentication> 

How to use the mode "Forms"? Insert the <Forms> tag, and fill in the appropriate attributes.

<authentication mode="Forms">  
   <forms name=" AuthenticationDemo" loginUrl="logon.aspx" protection="All" path="/"timeout="30" /> 
</authentication>

Question 24. What is the web API in ASP.NET?

Answer: It is a framework provided by Microsoft for writing https services. There are many frameworks available to build https-based services. They follow a common guideline of international standardization but with different flavors. For example, all frameworks must adhere to these status codes-

• 1xx - Informational Message
• 2xx - Successful
• 3xx - Redirection
• 4xx - Client Error
• 5xx - Server Error

Features

• It is lightweight and thus good for small devices also like tablets and smartphones.
• No tedious & extensive configuration like WCF REST is required.
• MediaTypeFormatter makes it easy to configure your API response type in a single line (JSON, XML, and so on).
• IIS Hosting dependency is no more, and it can be hosted in the application too.
• Easy and simple control with https features such as Caching, Versioning, request/response headers, and its various content formats.
• It supports content negotiation (deciding the best response data format that the client can accept).

Question 25. Describe application state management in ASP.NET.

Answer: Application Level State Management is used to maintain the state of all the users accessing the web forms present within the website. The value assigned for an application is considered an object. Application objects will not have any default expiration period. Whenever the web server has been restarted or stopped, then the information maintained by the application object will be lost. If any data is stored on the application object, then that information will be shared with all the users accessing the web server. Since the information is shared among all the users, it is advisable to lock and unlock the application object as per requirement.

Global Application Class(Global.asax)

It is a Class that consists of event handlers that execute the code implicitly whenever a relevant task has been performed on the web server.

<%@ Application Language="C#" %>  
    <script runat="server">  
    void Application_Start(object sender, EventArgs e)  
    {  
        // Code that runs on application startup  
    }  
    void Application_End(object sender, EventArgs e)  
    {  
        // Code that runs on application shutdown  
    }  
    void Application_Error(object sender, EventArgs e)  
    {  
        // Code that runs when an unhandled error occurs  
    }  
    void Session_Start(object sender, EventArgs e)  
    {  
        // Code that runs when a new session is started  
    }  
    void Session_End(object sender, EventArgs e)  
    {  
        // Code that runs when a session ends.   
    }  
    </script>

Question 26. What is the code behind an Inline Code?

Answer: Code Behind refers to the code for an ASP.NET Web page that is written in a separate class file that can have the extension of .aspx.cs or .aspx.vb depending on the language used. Here the code is compiled into a separate class from which the .aspx file derives. You can write the code in a separate .cs or .vb code file for each .aspx page. One major point of Code Behind is that the code for all the Web pages is compiled into a DLL file that allows the web pages to be hosted free from any Inline Server Code.

Inline Code

Inline Code refers to the code that is written inside an ASP.NET Web Page that has an extension of .aspx. It allows the code to be written along with the HTML source code using a <Script> tag. Its major point is that since it's physically in the .aspx file, it's deployed with the Web Form page whenever the Web Page is deployed.

Question 27. What is the ASP.NET page life Cycle?

Answer: When the user requests a page from the browser, the request goes through a series of steps, and many things happen in the background to produce the output or send the response back to the client. The periods between the request and response of a page are called the "Page Life Cycle".

• Request: Start of the life cycle (sent by the user).
• Response: End of the life cycle (sent by the server).

There are four stages that occur during the Page Life Cycle before the HTML Response is returned to the client. Later in this article, we"ll study all these stages and their sub-events.

1. Initialization
2. Loading
3. Rendering
4. Unloading

Initialization	During this stage, the IsPostback property is set. The page determines whether the request is a Postback (old request) or if this is the first time the page is being processed (new request). Controls on the page are available, and each control's UniqueID property is set. Now if the current request is a postback, then the data has not been loaded, and the value of the controls has not yet been restored from the view state.
Loading	At this stage, if the request is a Postback, then it loads the data from the view state.
Rendering	Before rendering, the View State is saved for the page and its controls. During this phase, the page calls the render method for each control, providing a text writer that writes its output to the OutputStream of the page's Response property.
Unloading	Unload is called after the page has been fully rendered, sent to the client, and is ready to be discarded. At this point also, the page properties such as Response and Request are unloaded.

Question 28. What are the ASP.NET page life cycle events?

Answer: We have many events in the ASP.NET page life cycle let’s see some most important events:

• Page request When ASP.NET gets a page request, it decides whether to parse and compile the page, or there would be a cached version of the page; accordingly, the response is sent,
• Starting of page life cycle At this stage, the Request and Response objects are set. If the request is an old request or post back, the IsPostBack property of the page is set to true. The UICulture property of the page is also set.
• Page initialization At this stage, the controls on the page are assigned a unique ID by setting the UniqueID property, and themes are applied. For a new request, postback data is loaded, and the control properties are restored to the view-state values.
• Page load At this stage, control properties are set using the view state and control state values.
• Validation Validate method of the validation control is called, and if it runs successfully, the IsValid property of the page is set to true.
• Postback event handling If the request is a postback (old request), the related event handler is called.
• Page rendering At this stage, the view state for the page and all controls are saved. The page calls the Render method for each control, and the output of rendering is written to the OutputStream class of the Page's Response property.
• Unload The rendered page is sent to the client, and page properties, such as Response and Request, are unloaded, and all cleanup is done.

ASP.NET Page Life Cycle Events

• PreInit PreInit is the first event in the page life cycle. It checks the IsPostBack property and determines whether the page is a postback. It sets the themes and master pages, creates dynamic controls, and gets and sets profile property values. This event can be handled by overloading the OnPreInit method or creating a Page_PreInit handler.
• Init Init event initializes the control property, and the control tree is built. This event can be handled by overloading the OnInit method or creating a Page_Init handler.
• InitComplete InitComplete event allows tracking of view state. All the controls turn on view-state tracking.
• LoadViewState LoadViewState event allows loading view state information into the controls.
• LoadPostData During this phase, the contents of all the input fields defined with the <form> tag are processed.
• PreLoad occurs before the post-back data is loaded in the controls. This event can be handled by overloading the OnPreLoad method or creating a Page_PreLoad handler.
• Load The Load event is raised for the page first and then recursively for all child controls. The controls in the control tree are created. This event can be handled by overloading the OnLoad method or creating a Page_Load handler.
• LoadComplete The loading process is completed, control event handlers are run, and page validation takes place. This event can be handled by overloading the OnLoadComplete method or creating a Page_LoadComplete handler.
• PreRender The PreRender event occurs just before the output is rendered. By handling this event, pages, and controls can perform any updates before the output is rendered.
• PreRenderComplete as the PreRender event is recursively fired for all child controls, this event ensures the completion of the pre-rendering phase.
• SaveStateComplete State of control on the page is saved. Personalization, control state, and view state information are saved. The HTML markup is generated. This stage can be handled by overriding the Render method or creating a Page_Render handler.
• UnLoad The UnLoad phase is the last phase of the page life cycle. It raises the UnLoad event for all controls recursively and, lastly, for the page itself. Final cleanup is done, and all resources and references, such as database connections, are freed. This event can be handled by modifying the OnUnLoad method or creating a Page_UnLoad handler.

Question 29. Describe login Controls in ASP.

Answer: The Login control provides the user interface to log a user into a website. The Login control uses the Membership service to authenticate the user in your membership system. The default Membership service from your configuration file will be used automatically, however, you can also set the Membership provider that you would like used as a property on the control. The Login Control consists of,

• Username Label and Textbox: Collects the string used to identify the user in the membership system.
• Password Label and Textbox: Collects the password for the specified user. The textbox text is always obscured.
• LoginButton: The button to submit the user's request for authentication.
• RememberMe: Configurable to display a checkbox giving the user the option to store a persistent cookie on the user's machine.
• Title and Instruction: Text to orient and guide the user through the process.
• Links: Configurable links to help, password recovery, and user registration information.
• Validators: Required field Validators for the username and password text boxes.

For Example

<asp:Login ID="Login1" runat="server" BackColor="#FFE0C0" BorderColor="Red" ></asp:Login>

Question 30. How to use repeater control in ASP.NET?

Answer: A Repeater is a Data-bound control. Data-bound controls are container controls. It creates a link between the Data Source and the presentation UI to display the data. The repeater control is used to display a repeated list of items. The main use of Repeater Control is for displaying a repeated list of items bound to the control. A Repeater Control is faster and more lightweight for displaying data compared to a GridView or DataGrid. With the Repeater control, we can display data in a custom format. The main drawback of a Repeater Control is that it doesn't support paging and sorting. The Repeater Control has the following types of template fields,

• Item Template
• AlternatingItem Template
• Header Template
• Footer Template
• Separator Template

Write connection code and select command in code behind file like:

protected void Page_Load(object sender, EventArgs e)  
{  
    SqlConnection con = new SqlConnection("Data Source=MCNDESKTOP34;Initial Catalog=yatendra;Persist Security Info=True;User ID=sa;  
        Password = Password$2 ");   
        SqlDataAdapter sda = new SqlDataAdapter("select * from Student_Details1", con); DataTable dt = new DataTable(); sda.Fill(dt); Repeater1.DataSource = dt; Repeater1.DataBind();  
} 

Now use the Repeater control object in the .aspx file like:

<asp:Repeater ID="Repeater1" runat="server">  
    <ItemTemplate>  
        <div>  
            <table>  
                <tr>  
                    <th>Student  
                        <%#Eval("S_ID")%>  
                    </th>  
                </tr>  
                <tr>  
                    <td>Student Name</td>  
                    <td>  
                        <%#Eval("Student_Name")%>  
                    </td>  
                </tr>  
                <tr>  
                    <td>Registration Number</td>  
                    <td>  
                        <%#Eval("Register_No")%>  
                    </td>  
                </tr>  
                <tr>  
                    <td>Date Of Birth</td>  
                    <td>  
                        <%#Eval("D_O_B")%>  
                    </td>  
                </tr>  
                <tr>  
                    <td>Date Of Examination</td>  
                    <td>  
                        <%#Eval("D_O_E")%>  
                    </td>  
                </tr>  
                <tr>  
                    <td>Department</td>  
                    <td>  
                        <%#Eval("Department")%>  
                    </td>  
                </tr>  
            </table>  
        </div>  
    </ItemTemplate>  
</asp:Repeater>

When you run this page, the output will look like this:

Question 31. What are the different methods of session maintenance in ASP.NET?

Answer: Session is a State Management Technique. A Session can store the value on the Server. It can support any type of object to be stored along with our own custom objects. A session is one of the best techniques for State Management because it stores the data as client-based, in other words, the data is stored for every user separately, and the data is secured also because it is on the server. We can set the session on one of the following 2 types of configuration files:

1. Machine Configuration file- Machine Configuration is applied for all applications.

2. Application Configuration file- It's applied for only application by application basis.

   

Session Mode In ASP.NET, there are 4 types of Session Mode. Off

We can disable the session mode for the entire application using the off mode.

According to performance and durability, the difference between InProc, State Server, and SQL Server is:

Session mode	Performance Durability
InProc	More(1 processor and 1 server) less.
State Server	Medium(n processor and 1 server) Medium
SQL Server	Less More

Question 32. What is the difference between session and caching?

Answer: The first main difference between session and caching is: a session is per-user based, but caching is not per-user based, So what does that mean? Session data is stored at the user level, but caching data is stored at the application level and shared by all the users. It means that it is simply session data that will be different for the various users for all the various users, session memory will be allocated differently on the server, but for the caching, only one memory will be allocated on the server, and if one user modifies the data of the cache for all, the user data will be modified.

Question 33. What is the difference between httpsContext.Current.Items and httpsContext.Current.Session in ASP.NET?

Answer: Session state is one of the popular state management techniques in the ASP.NET environment. Web developer people play with session storage every now and then. It’s pretty simple to manage a session if you understand the basic concept. Here is the syntax to do that

Session[“KEY”] =”Value”;  

Or

Session[index] = ”Value”; 

Let's have an example:

using System;
using System.Collections.Generic;  
using System.Linq;  
using System.Web;  
using System.Web.UI;  
using System.Web.UI.WebControls;  
namespace WebApp  
{  
    public partial class WebForm1: System.Web.UI.Page  
    {  
        protected void Page_Load(object sender, EventArgs e)  
        {  
            if(!IsPostBack)  
            {  
                httpsContext.Current.Items["Value"] = "Sourav Kayal in ITEM";  
                httpsContext.Current.Session["Value"] = "Sourav Kayal in SESSION";  
                Response.Write((string)(httpsContext.Current.Items["Value"]) + "<br>");  
                Response.Write((string)(httpsContext.Current.Session["Value"]));  
            }  
        }  
        protected void Button1_Click(object sender, EventArgs e)  
        {  
            Response.Write((string)(httpsContext.Current.Items["Value"]) + "<br>");  
            Response.Write((string)(httpsContext.Current.Session["Value"]));  
        }  
    }  
}

Question 34. What is the difference between Server.Transfer and Response.Redirect?

Answer: Both Response.Redirect and Server.Transfer methods are used to transfer a user from one web page to another web page. Both methods are used for the same purpose, but still, there are some differences as follows. The Response.Redirect method redirects a request to a new URL and specifies the new URL while the Server.Transfer method for the current request terminates the execution of the current page and starts the execution of a new page using the specified URL path of the page. Both Response.Redirect and Server.Transfer has the same syntax like:

Response.Redirect("UserDetail.aspx");  
Server.Transfer("UserDetail.aspx"); 

Before touching on more points, I want to explain some https status codes, these are important for the understanding of the basic differences between these two. The https status codes are the codes that the Web server uses to communicate with the Web browser or user agent.

Question 35. What are page directives in ASP.NET?

Answer: Basically, Page Directives are commands. These commands are used by the compiler when the page is compiled.

How to use the directives on an ASP.NET page?

It is not difficult to add a directive to an ASP.NET page. It is simple to add directives to an ASP.NET page.

You can write directives in the following format: <%@[Directive][Attributes]%> See the directive format, it starts with "<%@" and ends with "%>".

The best way is to put the directive at the top of your page. But you can put a directive anywhere on a page. One more thing, you can put more than one attribute in a single directive. Here is the full list of directives,

• @Page
• @Master
• @Control
• @Import
• @Implements
• @Register
• @Assembly
• @MasterType
• @Output Cache
• @PreviousPageType
• @Reference

Question 36. What is https Handler?

Answer: Every request into an ASP.NET application is handled by a specialized component known as an https handler. The https handler is the most important ingredient while handling ASP.NET requests. Examples: ASP.NET uses different https handlers to serve different file types. For example, the handler for the web Page creates the page and control objects, runs your code, and renders the final HTML. ASP.NET default handlers,

1. Page Handler (.aspx) - Handles Web pages.
2. User Control Handler (.ascx) - Handles Web user control pages.
3. Web Service Handler (.asmx) - Handles Web service pages.
4. Trace Handler (trace.axd) - Handles trace functionality.

Why we need to create our own https Handler: Sometimes we need to avoid the ASP.NET full page processing model, which saves a lot of overhead, as the ASP.NET web form model has to go through many steps such as creating web page objects, persisting view state, etc. What we are interested in is developing some low-level interface that provides access to objects like Request and Response but doesn't use the full control-based web form model discussed above.

Examples

1. Dynamic image creator - Use the System.Drawing classes to draw and size your own images.
2. RSS - Create a handler that responds with RSS-formatted XML. This would allow you to add RSS feed capabilities to your sites.
3. Render a custom image,
4. Perform an ad hoc database query,
5. Return some binary data.

All https handlers are defined in the <httpsHandlers> section of a configuration file which is nested in the <system.web> element.

<httpsHandlers>  
    <add verb="*" path="trace.axd" validate="true" type="System.Web.Handlers.TraceHandler" />  
    <add verb="*" path="*.config" validate="true" type="System.Web.httpsForbiddenHandler" />  
    <add verb="*" path="*.cs" validate="true" type="System.Web.httpsForbiddenHandler" />  
    <add verb="*" path="*.aspx" validate="true" type="System.Web.UI.PageHandlerFactory" /> </httpsHandlers>  

Question 37. What are the differences between ASP.NET httpsHandler and httpsModule?

Answer: The user requests a resource on a web server. The web server examines the file name extension of the requested file and determines which ISAPI extension should handle the request. Then the request is passed to the appropriate ISAPI extension. For example, when a .aspx page is requested, it is passed to the ASP.NET page handler.

Then Application domain is created, and after that, different ASP.NET objects like HTTP context, HTTPS request, and httpsResponse are created. Then an instance of httpsApplication is created, and also an instance of any configured modules. One can register different events of httpsApplication class like BeginRequest, AuthenticateRequest, AuthorizeRequest, ProcessRequest, etc.

https Handler

https Handler is the process that runs in response to an https request. So whenever a user requests a file, it is processed by the handler based on the extension. So, custom https handlers are created when you need special handling based on the file name extension. Let's consider an example to create RSS for a site. So, create a handler that generates RSS-formatted XML. Now bind the .rss extension to the custom handler.

https Modules

https Modules are plugged into the life cycle of a request. So when a request is processed, it is passed through all the modules in the pipeline of the request. So generally, https modules are used for,

• Security: For authenticating a request before the request is handled.
• Statistics and Logging: Since modules are called for every request, they can be used for gathering statistics and for logging information.
• Custom header: Since the response can be modified, one can add custom header information to the response.

Question 38. Explain the AdRotator Control

Answer: AdRotator controls are used to create dynamic ads. The AdRotator Control presents ad images each time a user enters or refreshes a webpage. When the ads are clicked, it will navigate to a new Web location. The AdRotator control is used to display a sequence of ad images. For the AdRotator control to work, we need an Advertisement file (XML file) and some sample images. Adding the AdRotator web server control to your web application. first, select the AdRotator and drag and drop the control to your web form. Map the XML file which contains the details about each and every ad. The advertisement file is an XML file. The following are some of the elements of this XML file.

1. <imageUrl>: Optional. The path to the image file.
2. <NavigateUrl>: Optional. The URL to link to if the user clicks the ad.
3. <AlternateText>: Optional. An alternate text for the image.
4. <Impressions>: Optional. The display rates in percent of the hits.

XML code that has the details about the ads. The file Ads.xml looks like the code below

<Advertisements>  
    <Ad>  
        <ImageUrl>adimages/2.jpg</ImageUrl>  
        <NavigateUrl>https://cat2.com</NavigateUrl>  
        <AlternateText>Cat 2</AlternateText>  
        <Impressions>30</Impressions>  
    </Ad>  
    <Ad>  
        <ImageUrl>adimages/3.jpg</ImageUrl>  
        <NavigateUrl>https://cat3.com</NavigateUrl>  
        <AlternateText>Cat 3</AlternateText>  
        <Impressions>20</Impressions>  
    </Ad>  
    <Ad>  
        <ImageUrl>adimages/4.jpg</ImageUrl>  
        <NavigateUrl>https://cat4.com</NavigateUrl>  
        <AlternateText>Cat 4</AlternateText>  
        <Impressions>10</Impressions>  
    </Ad>  
</Advertisements>

Question 39. What is cross-page posting in ASP.NET?

Answer: ASP.NET 1.1 provides for web forms to post back only to themselves. In many situations, the solution requires posting to a different web page. The traditional workaround alternatives were to use Response.Redirect and/or Server.Transfer to move to a different page and simulate cross-page post-back behavior. ASP.NET 2.0 provides a feature known as Cross Page PostBack for a web form to post back to a different web form (other than itself).

How to post to a different page?

To set a web form to post back to a different web form, in the source web form, set the PostBackURL property of the control that implements IButtonControl (eg. Button, ImageButton, LinkButton) to the target web form. When the user clicks on this button control, the web form is cross-posted to the target web form. No other settings or code is required in the source web form.

Access source page info within the posted page: FindControl Method

The target web form resulting from the cross-page postback provides a non-null PreviousPage property. This property represents the source page and provides a reference to the source web form and its controls. The controls on the source page can be accessed via the FindControl method on the object returned by the PreviousPage property of the target page.

protected void Page_Load(object sender, EventArgs e)  
{  
   ...  
   TextBox txtStartDate = (TextBox) PreviousPage.FindControl("txtStartDate ");  
   ...  
}

At this point, the target page does not have any knowledge of the source page. The PreviousPage property is of the type Page. For accessing controls using FindControl, the developer has to presume a certain structure in the source web form. This approach using FindControl has a few limitations. FindControl is dependent on the developer to provide the ids of the controls to access. The code will stop working if the control id is changed in the source web form. The FindControl method can retrieve controls only within the current container. If you need to access control within another control, you need to first get a reference to the parent control.

Access source page info within the posted page: @PreviousPageType Directive

There is another more direct option to get access to the source page controls if the source page is pre-determined. The @PreviousPageType directive can be used on the target page to type the source page strongly. The directive specifies the source page using either the VirtualPath attribute or the TypeName attribute. The PreviousPage property then returns a strongly typed reference to the source page. It allows access to the public properties of the source page.

SourcePage.aspx

<form runat="server"> ...  
    <asp:textbox runat="server" id="txtFirstName" />  
    <asp:textbox runat="server" id="txtLastName" />  
    <asp:button runat="server" id="btnViewReport" Text="View Report" PostbackURL="~/targetpage.aspx" /> ... public string FirstName { get { return txtFirstName.Text; } } ...  

TargetPage.aspx

<%@ PreviousPageType VirtualPath="sourcepage.aspx" %>  
string strFirstName;  
strFirstName = PreviousPage.FirstName; //Strongly Typed PreviousPage allows direct access to the public properties of the source page  

Question 40. Explain GridView control in ASP.NET

Answer: The GridView control displays the values of a data source in a table. Each column represents a field, while each row represents a record. The GridView control supports the following features,

• Binding to data source controls, such as SqlDataSource.
• Built-in sort capabilities.
• Built-in update and delete capabilities.
• Built-in paging capabilities.
• Built-in row selection capabilities.
• Programmatic access to the GridView object model to dynamically set properties, handle events, and so on.
• Multiple key fields.
• Multiple data fields for the hyperlink columns.
• Customizable appearance through themes and styles.

Creating a GridView

<asp:GridView ID="gridService" runat="server">  
</asp:GridView> 

Question 41. What is the difference between ASP.NET Web API and WCF?

Answer: The ASP. NET Web API is a framework that uses the https services and makes it easy to provide the response to the client request. The response depends on the request of the clients. The Web API builds the https services and handles the request using the https protocols. The request may be GET, POST, DELETE, or PUT. We can also say that the ASP. NET Web API:

• It is an https service.
• It is designed for reaching a broad range of clients.
• Uses the https application.

We use the ASP. NET Web API for creating the RESTful (Representational State Transfer) services. The following are some important points of the ASP. NET Web API,

• The ASP. NET Web API supports the MVC application features that are controller, media formats, routing, etcetera.
• It is a platform for creating REST services.
• It is a framework for creating the https services.
• Responses can be formatted by the APIs MediaTypeFormatter into the JavaScript Object Notation (JSON) and Extensible Markup Language (XML) formats.

Question 42. What is the PostBack property in ASP.NET?

Answer: If we create a web page, which consists of one or more Web Controls configured to use AutoPostBack (every Web control will have its own AutoPostBack property), the ASP.NET adds a special JavaScipt function to the rendered HTML Page. This function is named _doPostBack(). When Called, it triggers a PostBack, sending data back to the web Server. ASP.NET also adds two additional hidden input fields that are used to pass information back to the server. This information consists of the ID of the Control that raised the event and any additional information if needed. These fields will empty initially, as shown below,

<input type="hidden" name="__EVENTTARGET" id="__EVENTTARGET" value="" />  
<input type="hidden" name="__EVENTARGUMENT" id="__EVENTARGUMENT" value="" />   

The following actions will be taken place when a user changes a control that has the AutoPostBack property set to true:

1. On the client side, the JavaScript _doPostBack function is invoked, and the page is resubmitted to the server.
2. ASP.NET re-creates the Page object using the .aspx file.
3. ASP.NET retrieves state information from the hidden view state field and updates the controls accordingly.
4. The Page.Load event is fired.
5. The appropriate change event is fired for control. (If more than one control has been changed, the order of change events is undetermined.)
6. The Page.PreRender event fires and the page is rendered (transformed from a set of objects to an HTML page).
7. Finally, the Page.Unload event is fired.
8. The new page is sent to the client.

Question 43. Explain Cookie-less Session in ASP.NET.

Answer: By default, a session uses a cookie in the background. To enable a cookie-less session, we need to change some configurations in the Web.Config file. Follow these steps,

1. Open Web.Config file.
2. Add a <sessionState> tag under <system.web> tag.
3. Add an attribute "cookieless" in the <sessionState> tag and set its value to "AutoDetect" like below:

<sessionState cookieless="AutoDetect" regenerateExpiredSessionId="true"/> 

The possible values for the "cookieless" attribute are,

• AutoDetect: Session uses background cookie if cookies are enabled. If cookies are disabled, then the URL is used to store session information.
• UseCookie: Session always uses a background cookie. This is the default.
• UseDeviceProfile: Session uses a background cookie if the browser supports cookies else, URL is used.
• UseUri: Session always uses URL.

"regenerateExpiredSessionId" is used to ensure that if a cookieless URL is expired, a new URL is created with a new session. And if the same cookieless URL is being used by multiple users at the same time, they all get a new regenerated session URL.

Question 44. What are the Themes in ASP.NET?

Answer: A theme decides the look and feel of the website. It is a collection of files that define the looks of a page. It can include skin files, CSS files & images. We define themes in a special App_Themes folder. Inside this folder are one or more subfolders named Theme1, Theme2, etc., that define the actual themes. The theme property is applied late in the page's life cycle, effectively overriding any customization you may have for individual controls on your page.

How to apply themes in ASP.NET?

There are 3 different options to apply themes to our website,

1. Setting the theme at the page level: the Theme attribute is added to the page directive of the page.

   <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs"Inherits="Default" Theme="Theme1"%>  

2. Setting the theme at the site level: to set the theme for the entire website, you can set the theme in the web.config of the website. Open the web.config file and locate the <pages> element, and add the theme attribute to it:

   <pages theme="Theme1">  
      ....  
      ....  
   </pages>

3. Setting the theme programmatically at runtime: here, the theme is set at runtime through coding. It should be applied earlier in the page's life cycle ie. Page_PreInit event should be handled for setting the theme. The better option is to apply this to the Base page class of the site, as every page in the site inherits from this class.

   Page.Theme = Theme1; 

Uses of Themes in ASP.NET

1. Since themes can contain CSS files, images, and skins, you can change colors, fonts, positioning, and images simply by applying the desired themes.
2. You can have as many themes as you want, and you can switch between them by setting a single attribute in the web.config file or an individual aspx page. Also, you can switch between themes programmatically.
3. Setting the themes programmatically, you are offering your users a quick and easy way to change the page to their liking.
4. Themes allow you to improve the usability of your site by giving users with vision problems the option to select a high-contrast theme with a large font size.

Question 45. What are the Navigations techniques in ASP.NET?

Answer: Navigation can cause data loss if it is not properly handled. We have many techniques to transfer data from one page to another, but every technique has its own importance and benefits. We will discuss the following techniques in this article.

• Response.Redirect
• Server.Transfer
• Server.Execute
• Cross page posting

Question 46. What are WebParts in ASP.NET?

Answer: ASP.NET 2.0 incorporates the concept of WEB PARTS in itself, and we can code and explore that as easily as we have done with the other controls in the previous sessions. We can compose web parts pages from "web parts", which can be web controls, and user controls.

Component of Web Parts

The web parts consist of different components, like,

• Web Part Manager
• Web Part Zone
• CatLog Part
• CatLog Zone
• Connections Zone
• Editor Part
• Editor Zone

Web Part Zone

• Web Part Zone can contain one or more Web Part controls.
• This provides the layout for the Controls it contains. A single ASPX page can contain one or more Web Part Zones.
• A Web Part Control can be any of the controls in the toolbox or even the customized user controls.

Question 47. What are master pages?

Answer

Some points about Master Pages,

1. The extension of MasterPage is '.master'.
2. MasterPage cannot be directly accessed by the client because it just acts as a template for the other Content Pages.
3. In a MasterPage, we can have content either inside ContentPlaceHolder or outside it. Only content inside the ContentPlaceHolder can be customized in the Content Page.
4. We can have multiple masters in one web application.
5. A MasterPage can have another MasterPage as Master to it.
6. The content page content can be placed only inside the content tag.
7. Controls of MasterPage can be programmed in the MasterPage and content page, but content page control will never be programmed in MasterPage.
8. A master page of one web application cannot be used in another web application.
9. The MasterPageFile property of a web form can be set dynamically, and it should be done either in or before the Page_PreInit event of the WebForm. Page.MasterPageFile = "MasterPage.master". The dynamically set Master Page must have the ContentPlaceHolder whose content has been customized in the WebForm.
10. The order in which events are raised: Load (Page), a Load (Master), a LoadComplete (Page) i.e. if we want to overwrite something already done in the Load event handler of Master, then it should be coded in the LoadComplete event of the page.
11. Page_Load is the name of the method for the event handler for the Load event of Master. (it's not Master_Load).

Question 48. What is Data Cache in ASP.NET, and how to use it?

Answer: Data Cache is used to store frequently used data in the Cache memory. It's much more efficient to retrieve data from the data cache instead of a database or other sources. We need to use System.Web.Caching namespace. The scope of the data caching is within the application domain, unlike "session".

Every user is able to access this object. When a client requests the server, the server executes the stored procedure or function or selects statements on the SQL Server database then it returns the response to the browser. If we run it again, the same process will happen on the web server with the SQL server.

How to create a data cache?

Cache ["Employee"] = "DataSet Name" We can create data caching using Cache Keyword. It's located in the System.Web.Caching namespace. It's just like assigning value to the variable.

How to remove a Data Cache?

We can remove Data Cache manually.

//We need to specify the cache name  
Cache.Remove(String key); 

Question 49. Enterprise Library in ASP.NET?

Answer: Enterprise Library: It is a collection of application blocks and core infrastructure. An enterprise library is a reusable software component designed for assisting software developers. We use the Enterprise Library when we want to build application blocks intended for the use of developers who create complex enterprise-level applications.

Enterprise Library Application Blocks

Security Application Block

Security Application Block provides developers the ability to incorporate security functionality in the application. This application can use various blocks, such as authenticating and authorizing users against the database.

Exception Handling Application Block

This block allows the developers to create consistency for processing the error that occurs throughout the layers of the Enterprise Application.

Cryptography Application Block

Cryptography application blocks allow developers to add encryption and hashing functionality to the applications.

Caching Application Block

Caching Application Block allows developers to incorporate a local cache in the applications.

Question 50. How can we improve the Performance of an ASP.NET Web Page?

Answer: This is the most common question from the ASP.NET forum in any interview. In this post, I’m going to point out some of the important points that may help to improve performance. Here I used the word “improve performance” in the sense to decrease the loading time of the page. There are various reasons behind this. Some of them we look into from the “backend side” (Database side), and the rest of them we need to take care of on the “front-end” ((UI) side. For illustrative purposes, you have an ASP.NET Web site, and one of the aspx pages takes much time to load. Throughout this article, we are going to see how to decrease the loading time.

Back End (DB)

1. Try to check the Query performance - that is, how much time the query will take to execute and pull the records from DB. Then use SQL Server Profiler and Execution plan for that query so that you can come to a conclusion about which part took much time.
2. Check in every table (who are all part of the query) Index is created properly.
3. If your query involves a complex stored procedure, which in turn uses a lot of joins, then you should focus on every table. In some cases, the sub-query performs better than the joins.
4. If your web page involves paging concepts, try to move the paging concepts to SQL Server. I meant that based on the page count, the SP will return the records, instead of bringing the records as a whole.