All Dotnet Interview Questions 150-200

Question 151 – What is an ASP.NET Application and Page Life Cycle?

ASP.NET creates an environment which can process the request. i.e. creates application object, request, response and context objects
Once environment is created, the request is processed through a series of events which is processed by using modules, handlers and page objects. MHPM (Module, handler, page and Module event)

Question 152 – What are the Steps for ASP.net environment creation?

Step 1    IIS checks which ISAPI extension can server and pass to respective. e.g. aspx page to aspnet_isapi.dll
Step 2    If first request then ApplicationManager creates a Application Domain.
Step 3    App Domain will create hosting environment (HttpRuntime) object, then core objects like HttpContext, HttpRequest and HttpResponse will be created.
Step 4    Once core objects created, HttpApplication is created, if global.aspx is available then object for that will be created. global.asax file inherits from ‘HttpApplication’ class
Step 5    The HttpApplication object is then assigned to the core ASP.NET objects(HttpContext, HttpRequest and HttpResponse) to process the page.
Step 6    HttpApplication then starts processing the request by the following format HTTP module events, handlers and page events. (MHPM)
Step 7    (M: HttpModule): Client request processing starts. Used when we want to inject logic in events of ASP.NET pipeline. It is an event based processor. 6 important events we can utilize before page object is created BeginRequest, AuthenticateRequest, AuthorizeRequest, ResolveRequestCache, AcquireRequestState and PreRequestHandlerExecute. 
Step 8    (H: ‘HttpHandler’): Used when we want to inject logic based in file extensions like ‘.ASPX’, ‘.HTML’. It is an extension based processor. Once above 6 events fired, ASP.NET engine will invoke ProcessRequest event.
Step 9    (P: ASP.NET page): ASP.NET page object will be created. There are 6 important events - Init, Load, validate, event, render and unload. SILVER to remember the events S – Start , I – (Init) , L (Load) , V (Validate), E (Event) and R (Render).
Step 10    (M: HttpModule): Once the page object is executed and unloaded from memory, HttpModule provides post page execution events which can be used to inject custom post-processing logic. There are 4 important post-processing events PostRequestHandlerExecute, ReleaserequestState, UpdateRequestCache and EndRequest.

Question 153 – What is the ASP.NET Page Life Cycle?

Section	Event	Description
HttpModule	BeginRequest	Signals a new request; guaranteed to be raised on each request.
HttpModule	AuthenticateRequest	Signals Asp.Net runtime is ready to authenticate the user.
HttpModule	AuthorizeRequest	Signals Asp.Net runtime is ready to authorize the user.
HttpModule	ResolveRequestCache	Asp.Net runtime determines Page can be loaded from Cache or to load completely. Caching logic can be implemented here.
HttpModule	AcquireRequestState	Signals Asp.Net runtime is ready to acquire session variables.
HttpModule	PreRequestHandlerExecute	Before handling over the control to handler if we needed to perform any tasks.
HttpHandler	ProcessRequest	Write logic which needs to be executed as per page extensions.
Page	Init	Creating controls dynamically, in case you have controls to be created on runtime. Any setting initialization. Master pages and the settings. We do not have access toviewstate, postedvalues and neither the controls are initialized.
Page	Load	Asp.Net controls are fully loaded and write UI manipulation logic.
Page	Validate	Any valuators on your page, If we like to check the same here.
	Render	Like to make some changes to the final HTML which is going out to the browser, you can enter your HTML logic here.
Page	Unload	Page object is unloaded from the memory.
HttpModule	PostRequestHandlerExecute	Any logic you would like to inject after the handlers are executed.
HttpModule	ReleaserequestState	Like to save update some state variables like session variables.
HttpModule	UpdateRequestCache	Before you end, if you want to update your cache.
HttpModule	EndRequest	Last stage before your output is sent to the client browser.

Question 154 – What is a Directive in ASP.Net?

Directives specify settings that are used by the page and user-control compilers when the compilers process ASP.NET Web Forms pages and user control files. There are 11 types of directives in asp.net and are as follows

·         @Page - Enables you to specify attributes and values for an Asp.Net Page to be used when the page is parsed and compiled.

·         @Master - It is quite similar to the Page directive. The Master directive belongs to Master Pages that is .master files.

·         @Control - It is used when we build an Asp.Net user controls. The @Control directive helps us to define the properties to be inherited by the user control. These values are assigned to the user control as the page is parsed and compiled.

·         @Register - Associates aliases with namespaces and classes, which allow user controls and custom server controls to be rendered when included in a requested page or user control.

·         @Reference -  Links a page, user control, or COM control to the current page or user control declaratively.

·         @PreviousPageType - Creates a strongly typed reference to the source page from the target of a cross-page posting.

·         @OutputCache - It controls the output caching policies of the Asp.Net page or user control.

·         @Import - Imports a namespace into a page or user control explicitly.

·         @Implements - It gets the Asp.Net page to implement a specified .NET framework interface.

·         @Assembly - It is used to make your ASP.NET page aware of external components.

·         @MasterType - To access members of a specific master page from a content page, you can create a strongly typed reference to the master page by creating a @MasterType directive.

Question 155 – What are the different Validation Controls in ASP.Net?

·         Required Field Validator – Makes an input control as a required field.

·         Range Validator – Check that the users input falls under a specific range.

·         Compare Validator – Compare the value of 1 input control to other input control or to fixed value.

·         Regular Expression Validator – Ensure the value of 1 input control matches a specified pattern.

·         Custom Validator – we can write our own validation logic, e.g. we can check for values at run time.

·         Validation Summary – Displays report of all the validation errors of current page.

Question 156 – What is the Difference between User Control and Custom Control?

User Controls	Custom Controls
Easier to create	Harder to create
Complied at runtime	Pre-complied control
Cannot be added to tool box	Can be added to toolbox
Good for Static layout	Good for dynamic layout
Not complied in to dll	Complied into dll
HTML Design(Visual Design possible)	No Visual Design, HTML needs to be declared programmatically
One user control cannot be used in different projects	one custom control can be used in different projects

Question 157 – What is the Difference between Client Side and Server Side Code?

Client Side	Server Side
Code is written in a scripting language such as JavaScript andHTML	Code is written in VB, C# or other compiled languages
The browser itself executes the code in response to a user action and no server round trip is involved	Code is executed by the server during a roundtrip in response to a user request or action
Client browser executes code to dynamically modify the HTML.This is called Dynamic HTML	The server executes server side code and returns HTML code tothe client browser for display
Code is script and therefore it is interpreted	Code is either compiled dynamically or precompiled into assemblies

Question 158 – What is the Difference between Server.Transfer and Response.Redirect?

Server.Transfer	Response.Redirect
There is no Round trip	There is a Round trip
Previous page values are accessible	Previous page values are not accessible
Performance wise its better	Less performance
Information can be preserved in Server transfer through aparameter called preserveForm	A state can be maintained in Response redirect but has a lot ofdrawbacks

Question 159 – What are the different IIS Isolation Levels in ASP.Net?

IIS5 supports three isolation levels

·         Low (IIS Process)

§  ASP pages run in INetInfo.Exe, the main IIS process

§  ASP crashes, IIS crashes

·         Medium (Pooled)

§  ASP runs in a different process, which makes this setting more reliable

§  If ASP crashes IIS won't.

·         High (Isolated)

§  Each ASP application runs out-process in its own process space

§  If an ASP application crashes, neither IIS nor any other ASP application will be affected

Question 160 – What are the different Authentication Modes available in ASP.Net?

·         Windows

·         Form

·         Passport

·         None

Question 161 – What is Windows Authentication Mode in ASP.Net?

Windows Authentication mode relies upon IIS to perform the required authentication of a client. After IIS authenticates a client, it passes a security token to ASP.NET.

Question 162 - What are the advantages and disadvantages of Windows Authentication Mode?

Advantages - Authenticates using Windows accounts, so you do not need to write any custom authentication code.
Disadvantages - May require the use and management of individual Windows user accounts.

Question 163 – What is Form Authentication Mode in ASP.Net?

Form Authentication is an authentication scheme that makes it possible for the application to collect credentials using an HTML form directly from the client. If your application authenticates the client, it issues a cookie to the client

Question 164 - What are the advantages and disadvantages of Form Authentication Mode?

Advantages - Makes it possible for custom authentication schemes using arbitrary criteria. Can be used for authentication or personalization. It does not require corresponding Windows accounts.
Disadvantages - Is subject to replay attacks for the lifetime of the cookie, unless using SSL/TLS. Is only applicable for resources mapped to Aspnet_isapi.dll.

Question 165 – What is Passport Authentication Mode in ASP.Net?

Passport Authentication is a centralized authentication service provided by Microsoft that offers a single logon. When register with Passport, the Passport service grants a site-specific key. The server uses this key to encrypt and decrypt the query strings passed between the site and the Passport logon server.

Question 166 - What are the advantages and disadvantages of Passport Authentication Mode?

Advantages - Supports single sign-in across multiple domains. It is Compatible with all browsers.
Disadvantages - Places an external dependency for the authentication process.

Question 167 – What is None Authentication Mode in ASP.Net?

None Authentication Mode is used when users are not authenticated at all or if you plan to develop custom authentication code.

Question 168 - What are the advantages and disadvantages of None Authentication Mode?

Advantages - Offers total control of the authentication process providing the greatest flexibility. It also provides the highest performance if you do not implement an authentication method.
Disadvantages - Custom-built authentication schemes are seldom as secure as those provided by the operating system. It requires extra work to custom-build an authentication scheme.

Question 169 – What are the different IIS authentications available?

IIS provides a variety of authentication schemes:

·         Anonymous (enabled by default) - Anonymous authentication gives users access to the public areas of your Web site without prompting them for a user name or password.

·         Basic - username and password are transmitted in clear text

·         Digest - username and password are transmitted with encrypted format

·         Integrated Windows authentication (enabled by default) - NTLM authentication/ Kerberos V5

·         Client Certificate Mapping - A certificate is a digitally signed statement that contains information about an entity and the entity's public key, thus binding these two pieces of information together.

Question 170 – What is an Event Bubbling?

Server Controls like DataGrid, DataGridView, DataList etc have other controls inside them. 
A control can participate in event bubbling through two methods that it inherits from the base class System.Web.UI.Control. These methods are OnBubbleEvent and RaiseBubbleEvent.
Example an DataGridView can have an Textbox or an button inside it. These Child Controls cannot raise events by themselves, but they pass the event to the parent control (DataGridView), which is passed to the page as “ItemCommand” event. This process is known as Event Bubbling.

Question 171 – What are the differences between Machine.Config and a Web.Config files in Asp.Net?

Web.config	Machine.config
Machine level configuration	Application/folder level configuration
Can have more than one Web.config	Only one Machine.config
Web.config overrides the machine.config file	Same
Automatically installed when installing Visual Studio.	Created when creating an ASP.Net web application

Question 172 – What is an Authentication?

Authentication is a process of identifying a user based on their credentials (means user id and password). There are 5 types of authentication and are as below.

·         Password based authentication

·         Device based authentication

·         Biometric Authentication

·         Retina Scanners

·         Hand Scanners

Question 173 – What is an Authorization?

Authorization is a process of determining whether an authenticated user is allowed to access a specific resource or not.

Question 174 – What is an Impersonation?

·         It is the process of executing code in the context of another user identity.

·         It is the mechanism in the ASP.NET which decide under which account web application should be run.

·         By default Impersonation is off, we need to enable it in Web.config file.

·         By default all the ASP.NET applications run under the ASP.NET user account. If you set the impersonation to TRUE in the Web.config file then that application runs under the current user's account who has logged in that machine. <identity impersonate="true" /> 

·         We can use the impersonation in this two scenarios:

§  To give each web application different permissions.

§  To use existing Windows user permission.

·         These two scenario are fundamentally different. In the first one, impersonation defines a single, specific account. In this case, no matter what user access the application, and no matter what type of user-level security you use, the code will run under the account you've set. In the second one, the user must be authenticated by IIS. The web-page code will then execute under the identity of the appropriate user.

Question 175 – What is Autopostback event in ASP.Net?

It is the mechanism, by which the page will be posted Back to the server automatically based on some events in the web controls. 
Example - Dropdown Box web control has the property autopostback, if we set the property to true, when ever user selects a different value in the combo box, and event will be fired in the server. i.e. a request will be send to the server.
Autopostback - Property of the control
IsPostback - Property of the Page class
IsPostback is a property which returns Boolean value. It checks weather the page is posted back or not.

Question 176 – What is Tracing in ASP.Net

Tracing is a way to monitor the execution of your ASP.NET application. You can record exception details and program flow in a way that doesn't affect the program's output.
Page level Tracing - Enabled on a page-by-page basis by adding "Trace=true" to the Page directive 
Application Tracing - You can enable tracing for the entire application by adding tracing settings in web.config. In below example, pageOutput="false" and requestLimit="20"

Question 177 – What is Scavenging?

It is the process of deleting items from the cache when memory is scarce. Items are removed when they have not been accessed in some time or when items are marked as low priority when they are added to the cache. ASP.NET uses the CacheItemPriority object to determine which items to scavenge first. CacheItemPriority.High assigns a priority level to an item so that the item is least likely to be deleted from the cache.

Question 178 – What are Trace Listeners?

·         It is a class that listens for trace and debug messages from .NET applications.

·         Display messages to users by writing messages to files.

·         It can modify messages before displaying them, or even we can filter out the messages

·         It is common practice to simply log the message with possibly some formatting for easy readability.

·         It is derived from the System.Diagnostics.TraceListener base class.

·         The .NET Framework ships with three trace listeners:

§  EventLogTraceListener - logging messages to event logs.

§  DefaultTraceListener - logging messages to standard debug output such as debuggers.

§  TextWriterTraceListener - logging messages to text files.

Question 179 – What is the difference between Respose.Write and Response.Output.Write?

Response.Output.Write	Respose.Write
Formatted output will be displayed.	unformatted output will be displayed.
It gives String.Format-style formatted output.	It never gives like that.
It writes the HTTP Output Stream.	It writes the text stream
As per specified options it formats the string and then write to web page.	It just output a string to web page.

Question 180 – What is SmartNavigation?

·         It is the property that enables the individual controls to maintain focus between PostBack

·         The features of SmartNavigation property are namely:

·         Maintaining element focus between post backs

·         Eliminate page flash caused by page post back

·         Prevents each post back from being saved in the browser history

·         The scroll position of a Web page is maintained after PostBack.

·         Only the most recent Web page state is retained in the Web browser history folder.

Question 181 - What is a State Management in ASP.Net?

State management is the process by which you maintain state and page information over multiple requests for the same or different pages. There are 2 types State Management:

·         Client – Side State Management

·         Server – Side State Management

Question 182 - What are the different management objects available with Client & Server Side Stage Management?

Client – Side State Management

·         View State – Asp.Net uses View State to track the values in the Controls. You can add custom values to the view state. It is used by the Asp.net page framework to automatically save the values of the page and of each control just prior to rendering to the page. When the page is posted, one of the first tasks performed by page processing is to restore view state.

·         Control State – If you create a custom control that requires view state to work properly, you should use control state to ensure other developers don’t break your control by disabling view state.

·         Hidden fields – Like view state, hidden fields store data in an HTML form without displaying it in the user's browser. The data is available only when the form is processed.

·         Cookies – Cookies store a value in the user's browser that the browser sends with every page request to the same server. Cookies are the best way to store state data that must be available for multiple Web pages on a web site.

·         Query Strings - Query strings store values in the URL that are visible to the user. Use query strings when you want a user to be able to e-mail or instant message state data with a URL.

Server – Side State Management

·         Application State - Application State information is available to all pages, regardless of which user requests a page.

·         Session State –Information is available to all pages opened by a user during a single visit.

Both application state and session state information is lost when the application restarts. To persist user data between application restarts, you can store it using profile properties.

Question 183 - How to Pass values between pages?

We can use one of the below options to pass value between 2 pages in ASP.Net.

·         If the value is a String then we can use either one of the following: QueryString, PostBack, Cookies, Session, Cache, Application, Database

·         If the value is a Dataset or an object then we can use either one of the following: (Assuming DTO object not serialized) - Session, Application, Cache

Question 184 - What is a View State?

·         It is a built-in structure for automatically retaining values amongst multiple requests for the same page.

·         The viewstate is internally maintained as a hidden field on the page but is hashed.

·         View State is used to retain the state of server-side objects between post backs.

·         Controls perform well - Label, TextBox, CheckBox, RadioButton, and HyperLink

·         Controls perform less - DropDownList, ListBox, DataGrid, and DataList because of size and large data.

·         Making roundtrips to the server.

·         Item stored in Viewstate exist for the life of the current page. This includes PostBack (to the same page).

Question 185 - What are the Benefits of ViewState?

·         No server resources are required.

·         The values in view state are hashed, compressed, and encoded, thus representing a higher state of security than hidden fields

·         It is good for caching data in Web frame configurations because the data is cached on the client

·         Simple to use

Question 186 - What are the Limitations of ViewState?

·         Page loading and posting performance decreases when large values are stored.

·         Although view state stores data in a hashed format, it can still be tampered because it is stored in a hidden field on the page.

Question 187 - What is an EnableViewState in ASP.Net?

·         EnableViewState turns on the automatic state management feature that enables server controls to re-populate their values on a round trip.

·         Through EnableViewState=true /false we can define whether we have to maintain values of control in hidden fields when page is posted back again and again

·         For example, if you are binding a control to data on every round trip then you do not need the control to maintain its view state, since you will wipe out any re-populated data in any case.

·         Viewstate is enabled for all server controls by default. To disable it, set the EnableViewState property of the control to false.

Question 188 - What are Hidden Fields in ASP.Net?

·         These are html input control with hidden type that store hidden data in the html.

·         The data stored in hidden field is available when form processed on the server or using JavaScript.

·         Syntax - <input type="hidden" name="EVENTTARGET" id="EVENTTARGETID" value="" />

·         Can store only one value in their value property. The value is saved as a string so we need to Typecast.

·         There are two types of server control hidden fields -

§  System.Web.UI.WebControls.HiddenField

§  System.Web.UI.HtmlControls.HtmlInputHidden.

Question 189 - What are the Benefits of Hidden Fields in ASP.Net?

·         Easy to implement

·         Hidden fields are supported by all browsers

·         Faster access of information because data is stored on client side

·         No server resources are required.

Question 190 - What are the Limitations of Hidden Fields in ASP.Net?

·         Not secure because the data is stored on Client side so can be tampered creating a security hole

·         Decreases page performance if too many hidden fields(large data’s)

·         Only support single value and do not support rich structures as HTML.

·         Have to work around with delimiters etc to handle complex structures.

Question 191 - What are Hidden Frames in ASP.Net?

·         A hidden frame is a frame with 0 width and height, so that no one can see it.

·         You can run programs in there when you need to make a round trip to the server so that your main frame does not refresh.

·         To create one, you just use a frameset tag

·         A hidden frame is a complete document, e.g. IFRAME, that is not visible.

Question 192 - What are the Benefits of Hidden Frames in ASP.Net?

·         Hidden frames allow you to cache more than one data field.

·         The ability to cache and access data items stored in different hidden forms.

Question 193 - What are the Limitations of Hidden Frames in ASP.Net?

·         Not supported by all browsers

·         Stored data is not secured as it is stored on client's machine in the form of hidden fields.

Question 194 - What is a Cookie in ASP.Net?

·         It is a small bit of text that accompanies requests and pages as they go between the server and browser.

·         The cookie contains information the Web application can read whenever the user visits the site.

·         It provide a useful means in Web applications to store user-specific information.

·         Cookies are associated with a Web site, not with a specific page, so the browser and server will exchange cookie information no matter what page the user requests from your site.

·         Most browsers support cookies of up to 4096 bytes.

·         Most browsers allow only 20 cookies per site, so if you try to store more, the old cookies are discarded.

·         Maximum 300 cookies can be stored that will be accepted from all sites combined.

Question 195 - What are the examples of Cookie usage in ASP.Net?

·         Cookies are used for all sorts of purposes, all relating to helping the Web site remember you.

·         For example, a site conducting a poll might use a cookie simply as a Boolean value to indicate whether your browser has already participated in voting so that you don't vote twice.

·         A site that asks you to log on might use a cookie to tell itself that you've already logged on so that you don't have to keep entering your credentials.

Question 196 - What are the Types of Cookies in ASP.Net?

·         Persistent - Means the cookie will be expired as soon as the application is closed

·         Non Persistent - Even the application is closed the data will be remained as per the cookie timeout value.

Question 197 - What are the Benefits of Cookies in ASP.Net?

·         They are simple to use.

·         Light in size, thus occupy less memory.

·         Stores server information on client side

·         Data need not to be sent back to server.

·         Cookies persist for much longer period of time than a session.

Question 198 - What are the Limitations of Cookies in ASP.Net?

·         Since they are stored on the client side in plain text, they are not secure.

·         Number of cookies that can be stored and their size is limited.

·         They don't work if security level is set too high in browser.

·         Some people might just disable cookies on their browsers.

Question 199 - What is the relation between Cookies and Session State?

·         By default, ASP.NET uses a non-persistent cookie to store the session state.

·         If a user has disabled cookies on the browser, Session state cannot use a cookie to store the session ID and Session state doesn't work. - No cookie, No Session state.

Question 200 - What is a Cookieless Session in ASP.Net?

You can configure your application to store Session IDs not in a cookie, but in the URLs of pages in your site. By keeping the Session ID in the URL, ASP.NET stores the ID in the browser, in a manner of speaking, and can get it back when the user requests another page. Cookieless sessions can get around the problem of a browser that refuses cookies and allow you to work with Session state.
However, under some limited circumstances, if the user shares the URL with someone else — perhaps to email the URL to a colleague while the user's session is still active — then both users might end up sharing the same session, with unpredictable results.