Asp.net Interview Questions

1.  What is Asp.net?

Asp.net is a technology providing set of specifications towards web based application development, this technology comes with .net

Asp.net supports different types of web application

·       Normal Web Applications [webpage towards pc based browser].

·       Mobile Web Applications [Webpage towards mobile device micro browser]

·       Web Services [Developing business logic towards business to business implementation]

·       AJAX Web Application [Developing web pages with AJAX specifications, this will avoid complete page submission and reloading webpage]

2. What is page directive?

Directive is an instruction to server; it should be first statement with in webpage. Based on instruction server will do the required processing.

3. Webpage creation techniques supported by asp.net

Asp.net supports two techniques

·       In page Technique

·       Code behind Technique

In page Technique: when the logic part and coding part placed within a single file .asp x is called in page technique this is useful for migration projects.

Code behind Technique: placing design part into .asp x file and logic part into .cs or .vb file is called code behind technique this makes development faster and provides security for logic part.

4. Web server controls

These controls are very advanced controls compare to html server controls, this will support extensibility. Web server controls are classified into following things.

1.   Standard controls

2.   Validation controls

3.   Navigation controls

4.   Data controls

5.   Web parts controls

6.   Login controls

7.   AJAX extension controls

5. Page life Cycle Events

Set of subprograms executed to words each time of web page processing is called “page life cycle events”.

1.   Page Pre init: This will be executed before memory initialization for webpage attaching theme, master page dynamically to web page is possible using pre init event procedure.

2.    Page init: This will be executed when memory is initialized for web page

3.   Page load: This will be executed when submitted data and controls are loaded. Database connectivity, reading submitted data can be placed within page load.

4.   Page prerender: This will be executed before rendering HTML content for server side control. Control behavior can be changed before producing client side control.

5.   Page unload: This will be executed once memory is released for webpage. Closing database connection etc.

6. Validation control

ASP.net is providing set of controls to perform validations; this will reduce manual coding for developer and makes development faster.

ASP.net is providing 6 validation controls

1.   Required Field Validator: It doesn’t allow textbox blank.

2.   Range validator: it will validate textbox data with a particular range.

3.   Compare Validator: It supports three types of validations   i>. Data type checking ii> .Validating textbox data with a constant using relational operator.iii>.Comparing two textboxes using relational operator

4.   Regular Expression Validator: It will validate textbox data against particular expression.

5.   Custom Validator: Developer should provide logic to perform custom validations; this control supports client side validation and server side validation.

6.   Validation Summary : It will display all the error at one place

7. Style sheet

Style sheet is a set of characteristics can be applied to html tags to extend functionality. Style sheet can be classified into 3 types:

1.   Inline Style sheet

2.   Embedded Style sheet

3.   Cascading Style sheet

1. Inline Style sheet: The style sheet applied to particular occurrence of tag is called “Inline Style sheet”.

2. Embedded Style sheet: The style sheet with in webpage is called “Embedded Style sheet”.

3. Cascading Style Sheet: The style sheet with in css file is called “Cascading style sheet, this provides look & feel similar throughout website in different WebPages & maintenance will be easier.

8. What is state management?

Web server remembering information of client is called “State management”. This can be implemented using following techniques.

1.   Context

2.   Query String

3.   Cookies

4.   Session

5.   Application

6.   Cache

7.   View state

I.                  Context: The user information variables can be maintained from one webpage to another webpage using context when redirection is using Server. Transfer.

II.               Query String: The client information can be maintained from one webpage to another webpage when redirection is using Response. Redirect.

III.            Cookies: cookie is a small amount of memory used by web server within client system. The purpose is maintaining personal info of client with in client system to reduce burden on server.

Cookies can be classified into two types

1.   In memory cookie

2.   Persist ant cookie

1.   In memory cookie: The cookie placed within browser memory process in called “in memory cookies”. .net providing http cookie class for sending or reading cookies.

Example:

Http cookie object = new Http cookies (“n”); (sending cookies)

Object. Value=100;

Response. Append cookies (object);

Object=Request. Cookies [“n”]// Reading cookies

2.   Persist ant cookie: Cookie placed within hard disk               

Memory of client system is called persist ant cookie

Http Cookie object= new Http Cookies (“n”);

Object. Value=100;

Object. Expires= Date time. Now. Add Days (2);

IV. Session Memory: when client makes a first request, web server will allocate block of memory unique to client on server system, this is called as session memory. The session memory will be maintained by web server with the timeout of 20 minutes by default.

Example:

Session [“n”] =100 // it will place variable into session memory

Remove (key)// it will remove variable from session memory

Abandon () // It will close session

1.   What is session tracking?

Session tracking is the concept of web server identifying the session belonging to the client, this is implemented using in memory cookie concept.

Web server will allocate unique ID to each client called “Session ID”, this Session Id will be given to client browser. Web server can generate 2¹²⁰ unique session ID’s.

V. Application Memory.

When the website is started web server will allocate a block of memory on server system common to all client, this is called “Application Memory”. Application memory doesn’t have timeout, it will be maintained throughout the website is running. Application object is provided to access application memory from asp net page, this provides following methods:

·       Application[“n”]=100

·       Remove(key)

·       Remove all ()//it will remove all the variables from application memory.

·       Lock (): lock will lock application memory to particular client request.

·       Unlock (): unlock will release lock, this makes application

Memory  available to other client.

VI. Caching:

Caching is the concept of storing frequently used data into temporary memory for faster access. This is considered as optimization technique to improve the performance of Web server.

VII. View State:

9. Grid view control

Grid View will display multiple records in tabular format. These support different customizations like sorting, paging, editing….

Date source property of grid view requires memory location address where data is available. Data bind () method of grid view will arrange records in a tabular format for displaying to client.

Grid view is providing different types of fields for customization

·       Bound Field: it will display normal text

<asp: bound field header text=”Column heading” data field=”dataset table column name”></asp: bound field>

·       Template field: It is a container field for placing web server control into grid view.

<Asp: template field>

     <Item template>

        Place web server control

     </item template>

</asp: template field>

·       Image filed: to place image into the grid view

·       Hyperlink filed: To place hyperlink into the grid view

·       Command field: This will provide set of special buttons

   1. Select button: This button will execute selected index changed () event of grid view and provides row selected by user.

   2. Edit Button, Cancel Button, Delete Button.

9. Data list control:

Data list is not provided with predefined structure developer can customize required structure using collection of templates provided with data list.

·       Header template

·       Item template

·       Separator template

·       Footer template

·       Edit item template

The important template is Item Template it will contain record structure.

10. What is bubbled event?

Execution of parent control event procedure towards child control action is called bubbled event.

11. What is the difference between Repeater Vs Data list control

·       Repeater comes with less number of templates [no edit item template]. Whereas Data list comes with more number of templates.

·       Repeater doesn’t provide styles. Html tags to be used for formatting. Data list provides style for formatting.

·       Repeater supports only one record display in a row [no repeat column property] Data list supports more than one record in a row.

·       Repeater is light weight component, it consumes less memory resources and processing will be faster over data list control.

·       Data list and repeater doesn’t support sorting and paging.

12. List view control

This doesn’t provide build in structure for presenting data; developer should customize structure using templates.

This control is provided with Asp.net 3.5.

·       Layout Template

·       Item Template

·       Alternating Item Template

·       Edit Item Template.

·       List view= Data list or repeater+ sorting and paging.

13. What is Dataset serialization and De-serialization?

Serialization is the process of converting object into stream [bytes arrangement].

De-serialization is the process of constructing object using stream.

This is required in 2 cases

·       Persisting object on to hard disk

·       Transmission of object on network wire.

Persisting object requires explicit serialization and de serialization.

Dataset supports xml based serialization by providing following methods.

·       Write XML

·       Read XML

Write XML Method: For serialization

Write xml (“xml file path”, options)

Options:

Xmlwritemode.ignorescheme-It will perform serialization of only data without structure. This can be used to download XML document to client system.

Xmlwritemode.Writeschema:-It will perform serialization of structure and data. This can be used when the requirement is creating back dataset from xml content.

Xmlwritemode.diffgram:-It will perform serialization of old value and new values by maintaining the status of each record. This is called state full serialization. This is used for distributed technology like remoting and web services.

Read XML Methods: This will perform de-serialization

Readxml(“filepath”,options);

·       Xmlreadmode.ignoresechema

·       Xmlreadmode.readschema

·       Xmlreadmode.diffgram

·       Xmlreadmode.inferschema: It will apply structure based on type of data.

·       Xmlreadmode.auto: It will apply one of the options based on content present in XML Document.

14. Caching:-

Cashing is the concept of storing frequently used data into temporary memory for faster access. This is considered as optimization technique to improve the performance of Web Server. When the webpage requires database communication for presenting data and expected with more number of requests go will caching to reduce the processing burden of the web server.

Asp.net supports 3 types of caching:

·       Output Caching

·       Fragment Caching

·       Data Caching

Output Caching: Caching entire webpage output is called “Output Caching”. Output caching directive can be used to apply output caching to webpage.

<% @ Output cache duration=”n secs” varybyparam=”paramatername/name” varybycustom=”browser” verybyheader= ”accept-languag” location=”Server/Client/Server and client/downstream/any/none”….%>

·       Duration:-It will specify lifetime of cache content

·       Vary by par am:-Multiple cache content can be maintained for webpage based on parameters values submitted by client.

·       Vary by custom:-It supports maintaining multiple cache content based on browser type.

·       Vary by Header:-It supports maintaining multiple cache content based on culture-type. This is required for globalization website.

Fragment Caching: Portion of webpage applied with caching is called “Fragment Caching”. Each portion is a web user control, so fragment caching is possible using web user control.

Data Caching:-Caching memory variable like array, dataset, variables is called “Data caching”. Data caching provides application level state, it is similar to application memory state management.

15. What is the difference between Application Memory and Data Caching?

·       Application memory is not thread safe, where locking is required explicitly. Data caching is thread safe, where locking will be applied implicitly.

·       Application memory will apply lock to all the variables. Data caching will apply lock to the variable under processing.

·       Application memory doesn’t support releasing variable memory when website demands. Data caching will support releasing variables memory based on priority when web site demands this is called “scavenging”

·       Application memory doesn’t support expiry policies [defining life of variable]. Data caching supports expiry policies.

o  File based expire

o  Time based expire

o  SQL Cache dependency

·       File based expire: The life time of cache variable is based on time stamp of file or modification of file is called file based expire.

·       Time based expire: Life of cache variable is based on particular time period is called “time based expiry”. This can be classified into 2 types.

o  Absolute time expiry: lifetime of variable from storage time in cache is called absolute time expiry.

o  Sliding time expiry: life time of cache variable from last access is called sliding time expiry.

·       SQL Cache Dependency: The life of cache variable is based on database table manipulation is called “SQL cache dependency”. This requires 3 steps.

o  Configuring SQL Server to monitor table for manipulation using Example :-                    aspnet_regsql –U “sa” –P “ “ –d “inventory” -ed

o  Configuring website with cache manager service to receive notifications from SQL Server.

o  Placing variable into cache with SQL Cache Dependency.

15. Web user control:

The control created by developer is called “user defined control”, this provides reusability and batter maintenance. The control creation can be classified into 2 types

·       Web user control

·       Custom control

16. What is the difference between web user control and custom control?

·       Web user control is represented in the form of .ASCX [active server control], it is not a complied code, the control cannot be placed on Tool box, and it will be local to website.

·       Custom control is represented in the form of DLL, it is complied code, the control can be placed on Tool box, and it is global to set of websites.

·       Web user control supports caching where as custom control doesn’t support caching.

·       Web user control doesn’t support scratch level control creation. Custom control supports scratch level control creation[It is possible inheriting control class or web control class]

·       If the requirement is local to website or caching go with web user control else custom control

17. What are session state settings?

Session can be applied with 3 types of settings

1.   Session mode setting

2.   Cookie less session setting

3.   Optimization of session setting

Session mode setting: Asp.net supports 3 types of sessions

      I.            In proc Session

   II.            State Server Session

III.            SQL Server Session

In Proc Session: The session with in website memory under worker process is called “in proc session”.

In process session go with two problems:

·       No reliability: session will lost when website is restarted

·       No solutions for web forming: Web forming is a concept of running different websites on different web servers as a one unit. In web farming, one session cannot be maintained for client with in process session.

State Server Session: State server comes with .net installation as a service of operating system. This implementation requires 2 steps.

·       Start state server: start->run ---> services.msc ->ok then right click & select start.

·       Configuring the site to state server session web. Config…

<system.web>

<Session state Mode=”state server” state connection string=”TCPIP=127.0.0.1:42424”/>

<system.web>

Note: state connection string requires IP address of system in which state server is running and port number [42424] of state server.

·       State server supports in memory storage i.e. temporary storage.

·       Session will lost when state server is restarted and back up cannot be maintained. The solution is SQL Server session state.

SQL Server Session State: This provides persistent storage of sessions by maintaining in the form of table, this provides more reliability and requires more financial investment.

This requires 2 steps:

·       Configuring SQL Server table

·       Configuring Web site

·       Configuring SQL Server: .net is providing aspnet_regsql.exe utility to communicate with SQL Server for creating table towards session state.

Example -> aspnet_regsql –U “sa” –P “” –ssadd –sstype “c” –d “inventory”

It will create table with in inventory database

-ssadd:--- adding session state table

-sstype:--“p” table will be created within asp state database

                  “c” Table will be created within specified database using “-d” option.

·       Configuring website towards SQL Server session state:-

<system.web>

<session state mode=”SQL Server” SQL connection string=”user id=sa; password=; database=inventory; data source=syst” allow custom SQL Database=”true”/>

2. Cookie less session: When client browser is disabled cookies, in this case session will not be maintained for client. The solution is cookie less session. Cookie less session is a concept of providing Session ID to client by appending to URL; this is called “Munged URL”.

 This requires setting in web.config

<session state cookieless=”true” timeout=”30”/>

Note: cookie less session goes with security problem, it is not recommended when sensitive data is stored in session memory

3. Optimization of Session: - Optimization of session is the concept of making use session in a proper manner to improve performance of web server.

This can be applied at 2 levels

·       Web site level

·       Page level

Web site level: requires setting in web.config

<session state mode=”off/inproc……/>

Off->Sessions will not be created for client, this will reduce lot of burden on web server.

Page level: Requires option with page directive

<%@ page………..enable session state=”true[d]/false/read only” %>

18. Asp.net Security

Asp.net provides security in the form of 2 things

·       Authentication and Authorization

·       Membership

Authentication and Authorization: Authentication is the process of getting the credentials of client like name, password, security token etc.

Authorization is the process of verifying credentials to provide access to resources.

Asp.net supports 3 types of Authentications:

1.   Windows based Authentication

2.   Forms based Authentication

3.   Passport Authentication.

1.   Windows based Authentication: - Authenticating client based on network level login parameters is called “windows based authentication”. The security can be applied only to private website of organization.

Go to web.config

<authentication mode=”Windows”/>

Then select web configuration file

<system.web>

<Authorization>

<allow users=”manager”/>

<deny user=”*”/>

</Authorization>

2.   Forms Based Authentication: Authenticating client based on custom login page verifying credentials with database is called “Forms based authentication”.

This will be applicable to private website and public website. Web server will provide security token to client browser as an identity of authenticated client. This requires setting in web.config.

Example:

<Authentication mode=”Forms”>

<Forms name=”c1” login url=”login.aspx”>

</Forms>

</Authentication>

<Authorization>

<Deny user=”?”/>

</Authrization>

Submit button_click

{

    If (Textbox1.text==”kapil” && Textbox2.text==”Dev”)

   System.web.security.FormsAuthentication.RedirectFromLoginPage (Textbox1.text, C1.checked);

Else

Response. Write (“Invalid…..”);

RedirectFromLoginPage () method will perform 2 things

·       Redirecting client to requested page

·       Security token will be given to client browser.

Passport Authentication: Authenticating client based on passport security token provided by passport.com site is called “passport authentication”.

19. Web services

Web service is an application logic managed by web server, accessible to different applications based on open industry standards in platform independent way. Web services main target is integrating different vendor’s software’s; this provides heterogeneous application communication under heterogeneous platforms.

Web services complete designing is based on XML with the standards provided by W3C.

Web Services provides following standards:

·       WSDL [Web Services Description Language]

·       SOAP [Simple Object Access Protocol]

·       HTTP

·       UDDI [Universal Description Discovery Integration]

WSDL: - WSDL is an XML based language for arranging description of Web Service methods.

SOAP [Simple Object Access Protocol]: SOAP is a formatting protocol which provides a set of standards for arranging request and response to provide communication between client application and web service.

Structure of SOAP Message

·       SOAP Header will contain address of destination and authentication info if required.

·       SOAP Body will contain method call info or result of method execution

·       SOAP fault will contain error information if any.

What are the Web method attribute class options?

·       Description: This provides Web Service Method description to user.

·       Enable Session: True/False[d] by default Session tracking is disabled for web method it can be enabled by setting enable Session option true………………………………………………..

[Web Method (enable session =true)

Public void m1 ()

{   }

·       Message Name: Internally Web Method will be represented in the form of XML format identified by message name. By default message name is same as Web method name, this message name should be unique when web method is overloaded, provide message name explicitly.

[Web method (message name=”getprod1”)]

Public dataset get prods ()//method overloading

{

}

[Web method (message name=”getprod1”)]

Public dataset get prods (string name)//method //overloading

{

}

·       Cache duration: This will apply caching for web method

[Web Method (cache duration=”300”)]

Public dataset get prods ()

{          }

How to Securing Web Service

Securing web service is providing access to authorized users or securing transmission of data.

·       IP Address and Domain name restriction

·       SOAP Header Security

·       SSL[Secured Socket Layer]

IP Address and Domain name restriction: Providing access to web service based on IP Address or domain name of client system is called “IP Address & Domain name restriction Security.

Start-run-inetmgr-myservice.asmx properties then select File Security Tab Remove Anonymous Access then move to IP Address and Domain Name <- edit grant single computer give the IP Address[127.0.0.5] and click ok. Web service will be accessible to system IP Address 127.0.0.5.

SOAP Header Security: Providing access to web service method based on authentication is called “SOAP Header Security”. The authentication information will be arranged within SOAP Header of SOAP Message.

This requires two changes:

·       Including SOAP Header class within web service file.

·       Creating SOAP Header class object within client application to input authentication information.

Example:

Go to service.cs

Public class AUTHINFO: Soap Header

{           Public string username;

Public string password;

}

Public class service: web service

{

         Public AUTHINFO object=new AUTHINFO ();

         [Web Method (), Soap Header (“object”)]

         Public integer sum (integer a, integer b)

{

    Object. Must Understood=true;

    If (object. Username==”KAPIL” && object. Password==”dev”)

      {

Object. Did understand=true; //It is informing soap that authentication information is valid, SOAP will prepare soap message with result.

                                    Return (a + b);

      }

Else

{

Object. Did understand=false; //authentication information is not valid.

Return (0);

      }

}

SSL (Secure Socket Layer): SSL provides secure communication between client and web server, this is strongly recommended when sensitive data is transmitted between browser and web server. The secure communication is possible through encryption and decryption.

UDDI Registry [Universal Description Discovery Integration]

UDDI registry acts like search engine for web services this provides technical information of web services free web services and business oriented web services.

Example:

www.uddi.xml.org

www.seekda.com

What Web Services cannot do?

·       Attaching file to SOAP Message is not possible

·       Message Level security is not supported

·       Web services cannot be hosted outside the web server

·       Messaging is not supported by web services.

WCF [Windows Communication Foundation]

WCF is a very rich distributed technology provided with .net 3.0 WCF major concentrations is unifying different existing technologies under its roof. WCF is extensible framework and comes with built in infrastructure. This makes developer, administrator and architect job easier.

WCF is completely based on ABC analysis

Address: - It will specify where WCF service is available example:

net.tcp://server name: port number /service name

Http://servername:portnumber/servicename

WCF Service can be given with more than one address.

Binding: It will specify how WCF service provides communication

This will specify different encoding formats

Net Tcp Binding…………….Remoting

Basic Http Binding……………Web Services

WS Http Binding………………. WS default WCF service supports multiple binding.

Contract: It will specify what WCF service provides to client application [which interface, method exposing to client]

These 3 combine can be called as end point. WCF Service supports hosting outside IIS.

.net is providing an assembly towards WCF Service implementation.

                      System.ServiceModel.dll

                                         |

               System. Service Model Namespace

                                         |

                                    Classes

                                         |

                 Service Contract Attribute Class

               Operation Contract Attribute Class

                         Service Host Class

Interface can be exposed to client by declaring as Service Contract interface

Service Contract interface methods can be exposed to client by declaring as Operation Contract methods. It is similar to Web Method in web service.

Service Host class is required to host WCF Service outside IIS.

WCF Implementation requires 2 steps:

1.    Creating Server application for hosting WCF Service this requires 3 things

·       Creating Service Contract Interface

·       Creating WCF Service Class implementing Service Contract interface.

·       Hosting WCF Service Class. If it is hosted with IIS, Manual coding is not required outside IIS requires manual coding.

2.    Creating Client application to communicate with WCF Service. This requires generating proxy to communicate with WCF Service.

What are the binding supported by WCF.

·       MexTcpBinding will expose types of WCF Service [Exposing Meta data]

·       NetTcpBinding provides binary encoding , it is similar to remoting

·       Basic Http Binding provides XML encoding; it is similar to web Service.

What is .svc file in WCF?

Answer:

.svc file is a text file. This file is similar to ours .asmx file in web services.

This file contains the details required for WCF service to run it successfully.

This file contains following details:
1. Language (C# / VB)
2. Name of the Service
3. Where the service code resides

Example of .svc file

<%@ ServiceHost Language="C#/VB" Debug="true/false" CodeBehind="Service code files path" Service="ServiceName"