Net Interview Questions Quick Reference and FAQ docx

.Net Interview Questions
Quick Reference and FAQ

General questions specifically from IT and .NET interviews point of view. Best for
Fresher and students who want to have a feel of what .NET questions are asked in
multinational companies.

2011
Abhishek Goenka
CIBERSITES INDIA
Version 1.0

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ASP.Net Interview Questions

From constructor to destructor (taking into consideration Dispose() and the concept of non-
deterministic finalization), what are the events fired as part of the ASP.NET System.Web.UI.Page
lifecycle. Why are they important? What interesting things can you do at each?
As all of us know a request comes from Client (Browser) and sends to Server (we call it as Web server) in
turn server process the request and sends response back to the client in according to the client request.
But internally in the web server there is quite interesting process that happens. To get aware of that
process we should first of all know about the architecture of the IIS
It mainly consists of 3 Parts/Files
 Inetinfo.exec

 ISAPI Filer (Container for Internet Server Application Interface dlls),
 Worker Process (aspnet_wp.exe)

Inetinfo.exe is the ASP.Net request handler that handles the requests from the client .If it's for static
resources like HTML files or image files inetinfo.exe process the request and sent to client. If the request
is with extension aspx/asp, inetinfo.exe processes the request to API filter. ISAPI filter will have several
runtime modules called as ISAPI extensions. To process the request ISAPI filter takes the help of these
runtime modules. The runtime module loaded for ASP page is asp.dll. And for ASP.NET page it's
ASPNET_ISAPI.dll. From here the request is processed to the "worker process". Worker Process will have
several application domains.

Worker process sends the request to HTTPPIPE line.(HTTP Pipeline is nonetheless collection of .net
framework classes). HTTP Pipeline compiles the request into a library and makes a call to HTTP runtime
and runtime creates an instance of page class

public class File : System.Web.UI.Page
{}

ASP.Net web page is a class derived from page class, this page class resides in system.web.dll
After creating instance pf page class HTTP Runtime immediately invokes process request method of
page class

Page Req = new Page();
Req.ProcessRequest();

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Page Event
Typical Use
PreInit
Raised after the start stage is complete and before the initialization stage begins.

Use this event for the following:
 Check the IsPostBack property to determine whether this is the first time
the page is being processed. The IsCallback and IsCrossPagePostBack
properties have also been set at this time.

 Create or re-create dynamic controls.
 Set a master page dynamically.
 Set the Theme property dynamically.
 Read or set profile property values.
Init
Raised after all controls have been initialized and any skin settings have been
applied. The Init event of individual controls occurs before the Init event of the
page.
Use this event to read or initialize control properties.
InitComplete
Raised at the end of the page's initialization stage. Only one operation takes
place between the Init and InitComplete events: tracking of view state changes is

turned on. View state tracking enables controls to persist any values that are
programmatically added to the ViewState collection. Until view state tracking is
turned on, any values added to view state are lost across postbacks. Controls
typically turn on view state tracking immediately after they raise their Init event.

Use this event to make changes to view state that you want to make sure are
persisted after the next postback.
PreLoad
Raised after the page loads view state for itself and all controls, and after it
processes postback data that is included with the Request instance.
Load
The Page object calls the OnLoad method on the Page object, and then
recursively does the same for each child control until the page and all controls
are loaded. The Load event of individual controls occurs after the Load event of
the page.

Use the OnLoad event method to set properties in controls and to establish
database connections.
Control events
Use these events to handle specific control events, such as a Button control's
Click event or a TextBox control's TextChanged event.
LoadComplete
Raised at the end of the event-handling stage.
Use this event for tasks that require that all other controls on the page be
loaded.
PreRender
Raised after the Page object has created all controls that are required in order to
render the page, including child controls of composite controls. (To do this, the
Page object calls EnsureChildControls for each control and for the page.)

The Page object raises the PreRender event on the Page object, and then
recursively does the same for each child control. The PreRender event of
individual controls occurs after the PreRender event of the page.

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Use the event to make final changes to the contents of the page or its controls
before the rendering stage begins.
PreRenderComplete
Raised after each data bound control whose DataSourceID property is set calls its
DataBind method. For more information, see Data Binding Events for Data-
Bound Controls later in this topic.
SaveStateComplete
Raised after view state and control state have been saved for the page and for all
controls. Any changes to the page or controls at this point affect rendering, but
the changes will not be retrieved on the next postback.
Render
This is not an event; instead, at this stage of processing, the Page object calls this
method on each control. All ASP.NET Web server controls have a Render method
that writes out the control's markup to send to the browser.

If you create a custom control, you typically override this method to output the
control's markup. However, if your custom control incorporates only standard
ASP.NET Web server controls and no custom markup, you do not need to
override the Render method. For more information, see Developing Custom
ASP.NET Server Controls.

A user control (an .ascx file) automatically incorporates rendering, so you do not
need to explicitly render the control in code.
Unload
Raised for each control and then for the page.

In controls, use this event to do final cleanup for specific controls, such as closing
control-specific database connections.

For the page itself, use this event to do final cleanup work, such as closing open
files and database connections, or finishing up logging or other request-specific
tasks.

Although both Init and Load recursively occur on each control, they happen in reverse order. The Init
event (and also the Unload event) for each child control occur before the corresponding event is raised
for its container (bottom-up). However the Load event for a container occurs before the Load events for
its child controls (top-down). Master pages behave like child controls on a page: the master page Init
event occurs before the page Init and Load events, and the master page Load event occurs after the
page Init and Load events.

What is EnableViewStateMAC?
Setting EnableViewStateMac=true is a security measure that allows ASP.NET to ensure that the
viewstate for a page has not been tampered with. If on Postback, the ASP.NET framework detects that
there has been a change in the value of viewstate that was sent to the browser, it raises an error -
Validation of viewstate MAC failed.



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Use <%@ Page EnableViewStateMac="true"%> to set it to true (the default value, if this attribute is not
specified is also true) in an aspx page.

But this has a side effect: it also prevents multiple servers from processing the same ViewState. One
solution is to force every server in your farm to use the same key generate a hex encoded 64-bit or
128-bit <machineKey> and put that in each server's machine.config :
<! validation="[SHA1|MD5|3DES]" >
<machineKey validation="SHA1"
validationKey="F3690E7A3143C185A6A8B4D81FD55DD7A69EEAA3B32A6AE813ECEEC" />


What is the difference between asp:Label and asp:Literal control?
asp:Label control
asp:Label control is used to write text on the page with different formatting options like bold, italic,
underlined etc
asp:Literal control
Ideally Literal control is the rarely used control which is used to put static text on the web page. When it
is rendered on the page, it is implemented just as a simple text.
Unlike asp:Label control, there is no property like BackColor, ForeColor, BorderColor, BorderStyle,
BorderWidth, Height etc. of Literal control. That makes it more powerful, you can even put a pure HTML
contents into it.

What’s a SESSION and APPLICATION object?
Viewstate - Viewstate is a hidden fields in an ASP.NET page, contains state of those controls on a page
whose "EnableViewstate" property is "true".
You can also explicitly add values in it, on an ASP.NET page like:
Viewstate.Add( "TotalStudents", "87" );

Viewstate should be used when you want to save a value between different roundtrips of a single page
as Viewstate of a page is not accessible by another page. Because Viewstate renders with the page, it
consumes bandwidth, so be careful to use it in applications to be run on low bandwidth.
Session Variable - Session variables are usually the most commonly used. When a user visits a site, it's
sessions starts and when the user become idle or leave the site, the session ends. Session variables
should be used to save and retrieve user specific information required on multiple pages. Session
variables consumes server memory, so if your may have a huge amount visitors, use session very
carefully and instead of put large values in it try to put IDs and references
Application variables - Application variables are shared variables among all users of a web application.
Application variables behave like static variables and they are substitute of static variables as static
variables are stateless in web applications. Only shared values should be persisted in Application
variables, and as soon as they are not in use they should be removed explicitly.
Cache - Cache is probably the least used state feature of ASP.NET. Cache is basically a resource specific
state persistence feature, means unlike session it stick with resource instead of user, for instance: pages,

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controls etc. Cache should be used or frequently used pages, controls, and data structures. Data cache
can be used to cache frequently used list of values e.g. list of products
Cookies - Cookies are some values saved in browsers by the website to retrievable and use afterwards.
Usually cookies are used to help dynamic websites to identify visitors and retrieve their saved
preferences. Cookies are also used to facilitate auto login by persisting user id in a cookie save in user's
browser. Because cookies have been saved at client side, they do not create performance issues but
may create security issues as they can be hacked from browser.

What are the different types of caching?
CachingOutput Caching - We can use Page output for those page which content are relatively static. So

rather than generating the page on each user request we can cached the page using Page output
caching so that it can be access from cache itself. So, Instead of pages can be generated once and then
cached for subsequent request. Page output caching allows the entire content of a given page to be
stored in the cache.
<%@ Page Language="C#" %>
<%@ OutputCache Duration='300' VaryByParam='none' %>
Fragment caching - ASP.NET provides a mechanism for caching portions of pages, called page fragment
caching. To cache a portion of a page, you must first encapsulate the portion of the page you want to
cache into a user control. In the user control source file, add an OutputCache directive specifying the
Duration and VaryByParam attributes. When that user control is loaded into a page at runtime, it is
cached, and all subsequent pages that reference that same user control will retrieve it from the cache.
<!— UserControl.ascx —>
<%@ OutputCache Duration='60'
VaryByParam='none' %>
<%@ Control Language="'C#'" %>
Data Caching - Caching of data can dramatically improve the performance of an application by reducing
database contention and round-trips. Simply data caching store the required data in cache so that web
server did not send request to DB server every time for each and every request which increase the web
site performance.
There are three Different ways to add data or object into cache. But based upon the situation we have
to access it. These methods are Cache[], Cache.add(), cache.insert(). The following table will show you
the clear difference of these methods.


Is it possible to prevent a browser from caching an ASPX page?
Just call SetNoStore on the HttpCachePolicy object exposed through the Response object's Cache
property, as demonstrated here:

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What does AspCompat="true" mean and when should I use it?
The AspCompat attribute forces the page to execute in STA mode. The runtime throws an exception if
the compatibility tag is omitted and an STA component is referenced on the page. If you convert the STA
component to an assembly using Tlbimp.exe, the runtime does not detect that the component uses the
STA model and does not throw an exception, but your application can suffer from poor performance.
<%@Page AspCompat=true Language = VB%>


What are the main event handlers in Global.asax?
ASP.NET provides several modules that participate in each request and expose events you can handle in
Global.asax. You can customize and extend these modules as you like, or develop completely new
custom modules to process information for and about HTTP requests made to your ASP.NET-based
application. Following are important events catered for in the Global.asax file.
 Application_Init: Fires when the application initializes for the first time.
 Application_Start: Fires the first time an application starts.
 Session_Start: Fires the first time when a user’s session is started.
 Application_BeginRequest: Fires each time a new request comes in.
 Application_EndRequest: Fires when the request ends.
 Application_AuthenticateRequest: Indicates that a request is ready to be authenticated.
 Application_Error: Fires when an unhandled error occurs within the application.
 Session_End: Fires whenever a single user Session ends or times out.
 Application_End: Fires when the application ends or times out (Typically used for application
cleanup logic).

What are different types of directives in .NET?
@Page: Defines page-specific attributes used by the ASP.NET page parser and compiler. Can be included
only in .aspx files <%@ Page AspCompat="TRUE" language="C#" %>
@Control: Defines control-specific attributes used by the ASP.NET page parser and compiler. Can be
included only in .ascx files. <%@ Control Language="VB" EnableViewState="false" %>


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@Import: Explicitly imports a namespace into a page or user control. The Import directive cannot have
more than one namespace attribute. To import multiple namespaces, use multiple @Import directives.
<% @ Import Namespace="System.web" %>
@Implements: Indicates that the current page or user control implements the specified .NET framework
interface.<%@ Implements Interface="System.Web.UI.IPostBackEventHandler" %>
@Register: Associates aliases with namespaces and class names for concise notation in custom server
control syntax.<%@ Register Tagprefix="Acme" Tagname="AdRotator" Src="AdRotator.ascx" %>
@Assembly: Links an assembly to the current page during compilation, making all the assembly's classes
and interfaces available for use on the page. <%@ Assembly Name="MyAssembly" %><%@ Assembly
Src="MySource.vb" %>
@OutputCache: Declaratively controls the output caching policies of an ASP.NET page or a user control
contained in a page<%@ OutputCache Duration="#ofseconds" Location="Any | Client | Downstream |
Server | None" Shared="True | False" VaryByControl="controlname" VaryByCustom="browser |
customstring" VaryByHeader="headers" VaryByParam="parametername" %>
@Reference: Declaratively indicates that another user control or page source file should be dynamically
compiled and linked against the page in which this directive is declared.

What are ASHX files? What are HttpHandlers? Where can they be configured?

ASP.NET programming supports the creation of custom HttpHandler components, which provide a
flexible and efficient way to process requests that don't return standard HTML-based pages. For
example, HttpHandler components are great for situations in which you want to return simple text,
XML, or binary data to the user.
The easiest way to create a custom HttpHandler component is to create a source file with an .ashx
extension. You must then add a @WebHandler directive to the top of the .ashx file, along with a class
definition that implements the IHttpHandler interface. Any class that implements the IHttpHandler
interface must provide an implementation of the IsReusable method and the ProcessRequest method.
<%@ Assembly Name="Microsoft.SharePoint, [full assembly name]" %>
<%@ WebHandler Language="C#" Class="HelloHttpHandler" %>
using System;
using System.Web;
using Microsoft.SharePoint;

public class HelloHttpHandler : IHttpHandler {
public bool IsReusable {
get { return false; }
}
public void ProcessRequest(HttpContext context) {
SPSite siteColl = SPContext.Current.Site;
SPWeb site = SPContext.Current.Web;
context.Response.ContentType = "text/plain"
context.Response.Write("Hello HttpHandler from the site " +
site.Title +
" at " +
site.Url);
}
}

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After you deploy your .ashx file within a directory nested within the \LAYOUTS directory, it is accessible
to any site in the farm by using a site-relative path.
http://MyWebServer/sites/Sales/_layouts/Litware/HelloHttpHandler.ashx


What is needed to configure a new extension for use in ASP.NET? For example, what if I wanted my
system to serve ASPX files with a *.jsp extension?
It is possible to configure new extension for use in ASP.Net. This as to be configured in IIS actually in
order for IIS to route your pages to the proper ISAPI
Follow this: />0.aspx


What events fire when binding data to a data grid? What are they good for?
ItemCreated: The ItemCreated event is fired when an item in a DataGrid control is created. This means
that at the time the event is fired, the DataGrid does not yet know about the data that will be bound to
it. So, if the logic of your method depends on this data being available to the control, you’re better off
using the ItemDataBound event. Other than that, the ItemCreate event differentiates itself in one other
way from the ItemDataBound event: the ItemCreated event is raised when data is bound to the control
and during round-trips (postbacks). These qualities make the event especially well-suited to add custom
attributes to a DataRow (such as onmouseover or other javascript events) or to control the appearance
in ways that do not depend on the data within the DataRow (such as making every 10th row a different
color).
ItemDataBound: The ItemDataBound event is fired after after an item in a DataGrid control is bound.
This means that (unlike the ItemCreated event) you can add special formatting to a DataRow that is
dependent upon the data contained within that row. Since ItemDataBound is fired after the

ItemCreated event, it is within this event that you are presented with the final opportunity to access the
data before it is rendered to the client. These qualities make the event well-suited for changing the
appearance of a row or cell based on the data within that row or cell (such as highlighting outliers or
other important information).Example:
Assume we have the following DataGrid declared on our .aspx page:
<asp:DataGrid ID="MainDataGrid"
runat="server"
AutoGenerateColumns="true"
OnItemDataBound="MainDataGrid_ItemDataBound"
OnItemCreated="MainDataGrid_ItemCreated" />
On the code behind page then, we can create the following two methods to handle adding
titles to header row, to specify more descriptive headers, and to change the row background
color based on an employee’s salary:

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protected void MainDataGrid_ItemCreated(object sender, DataGridItemEventArgs e)
{
//If the item is in the header
if (e.Item.ItemType == ListItemType.Header)
{
//Iterate through each cell
foreach(TableCell item in e.Item.Cells)
{
//Add the title attribute — we could just as easily
//add a javascript onmouseover event here
item.Attributes.Add("title", item.Text);

}
//Since the header values are set before we have access
//to the data, we can modify the third column header to
//be a bit more descriptive
e.Item.Cells[2].Text = "Salary (in US$)";
}
}

protected void MainDataGrid_ItemDataBound(object sender, DataGridItemEventArgs e)
{
//Since DataGrid differentiates between Items and AlternatingItems, you sometimes
have to check
//for one *or* the other

if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.Alternating
Item)
{
//Here we will modify the row color based on the salary
//We can only do this within ItemDataBound since it relies
//on the data being available from the data source
if (Convert.ToInt32(e.Item.Cells[2].Text) < 10000)
{
e.Item.BackColor = System.Drawing.Color.LightPink;
}
else if (Convert.ToInt32(e.Item.Cells[2].Text) < 1000000)
{
e.Item.BackColor = System.Drawing.Color.LightBlue;
}
else
{

e.Item.BackColor = System.Drawing.Color.LightGreen;
}
}
}





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ASP.NET Code Block Types
Interaction with the page from these blocks is limited, since the code is executed during the render
phase of the page life cycle
<% Trace.Warn("Embedded Code Block", "Hello World"); %>

Let’s have a look at the different types of syntax we can use for code blocks in ASP.NET pages. There are
really four types of code blocks, and the first one is different from the others:
 <%$ %>
 <%# %>
 <% %>
 <%= %>
ASP.NET Expression Syntax
First of all we have ASP.NET expressions which look like <%$ AppSettings:Key %>
<asp:Label runat="server" Text="<%$ AppSettings:Key %>" />
ASP.NET Data-Binding syntax
The next code construct is the data-binding syntax: <%# Eval("Value") %> which is used to bind to

properties to data on demand.
Statement and Expression/Evaluated Code Blocks
Display some values
<%
string message = "Hello World!";
Response.Write(message);
%>
These are delimited by <%= and %> and the content of this code block becomes the parameter to the
HtmlTextWrite.Write() method. Therefore, the code inside this type of code block should be an
expression, and not a statement.
<%= String.Format("The title of this page is: {0}", this.Title ?? "n/a") %>

What method do you use to explicitly kill a user s session?
Session.Abandon

Which two properties are on every validation control?
1. ControlToValidate
2. ErrorMessage

What are the validation controls in asp.net?
There are 5 validation controls in asp.net

1. RequiredFieldValidator
2. RangeValidator
3. RegularExpressionValidator
4. CompareValidator
5. CustomValidator

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ValidationSummary is not a validation control but a control that displays summary of all error occurs
while validating the page.

How to load a user control dynamically in runtime?
Control c = (Control)Page.LoadControl("~/usercontrol/MyUserControl.ascx");
Page.Form.Controls.Add(c);

How to get the authentication mode from web.config file programmatically at runtime?
System.Web.Configuration.AuthenticationSection section =
(AuthenticationSection)WebConfigurationManager.GetSection("system.web/authentication");
Label1.Text = section.Mode.ToString();

What’s the difference between Response.Write() and Response.Output.Write()?
Response.Output.Write() allows you to write formatted output.

What’s a bubbled event?
When you have a complex control, like DataGrid, writing an event processing routine for each object
(cell, button, row, etc.) is quite tedious. The controls can bubble up their event handlers, allowing the
main DataGrid event handler to take care of its constituents.

ASP.NET Compilation Tool (Aspnet_compiler.exe)
The ASP.NET Compilation tool (Aspnet_compiler.exe) enables you to compile an ASP.NET Web
application, either in place or for deployment to a target location such as a production server. In-place
compilation helps application performance because end users do not encounter a delay on the first
request to the application while the application is compiled.

Compilation for deployment can be performed in one of two ways: one that removes all source files,
such as code-behind and markup files, or one that retains the markup files.

What is different between WebUserControl and in WebCustomControl?
Web user controls :- Web User Control is Easier to create and another thing is that its support is limited
for users who use a visual design tool one good thing is that its contains static layout one more thing a
separate copy is required for each application.
Web custom controls: - Web Custom Control is typical to create and good for dynamic layout and
another thing is that it has full tool support for user and a single copy of control is required because it is
placed in Global Assembly cache.

What is smart navigation?
Enable smart navigation by using the Page.SmartNavigation property. When you set the
Page.SmartNavigation property to true, the following smart navigation features are enabled:

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 The scroll position of a Web page is maintained after postback.
 The element focus on a Web page is maintained during navigation.
 Only the most recent Web page state is retained in the Web browser history folder.
 The flicker effect that may occur on a Web page during navigation is minimized.
Note: Smart navigation is deprecated in Microsoft ASP.NET 2.0 and is no longer supported by Microsoft
Product Support Services


How many types of cookies are there in ASP.NET ?
 In-memory cookies: An in-memory cookie goes away when the user shuts the browser down.

 Persistent cookies: A persistent cookie resides on the hard drive of the user and is retrieved
when the user comes back to the Web page.

If you create a cookie without specifying an expiration date, you are creating an in-memory cookie,
which lives for that browser session only. The following illustrates the script that would be used for an
in-memory cookie:
Response.Cookies("SiteArea") = "TechNet"

The following illustrates the script used to create a persistent cookie:
Response.Cookies("SiteArea") = "TechNet"
Response.Cookies("SiteArea").Expires = "August 15, 2000"


TODO List
Explain how PostBacks work, on both the client-side and server-side. How do I chain my own JavaScript?
How does ViewState work and why is it either useful or evil?
What is the OO relationship between an ASPX page and its CS/VB code behind file in ASP.NET 1.1? In
2.0?
What happens from the point an HTTP request is received on a TCP/IP port up until the Page fires the
On_Load event?
How does IIS communicate at runtime with ASP.NET? Where is ASP.NET at runtime in IIS5? IIS6?
What is an assembly binding redirect? Where are the places an administrator or developer can affect
how assembly binding policy is applied?
Compare and contrast LoadLibrary(), CoCreateInstance(), CreateObject() and Assembly.Load().

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ASP.NET MVC 3 Interview Questions
What is MVC?
MVC is a framework methodology that divides an application’s implementation into three component
roles: models, views, and controllers.
“Models” in a MVC based application are the components of the application that are responsible for
maintaining state. Often this state is persisted inside a database (for example: we might have a Product
class that is used to represent order data from the Products table inside SQL).
“Views” in a MVC based application are the components responsible for displaying the application’s
user interface. Typically this UI is created off of the model data (for example: we might create an
Product “Edit” view that surfaces textboxes, dropdowns and checkboxes based on the current state of a
Product object).
“Controllers” in a MVC based application are the components responsible for handling end user
interaction, manipulating the model, and ultimately choosing a view to render to display UI. In a MVC
application the view is only about displaying information – it is the controller that handles and responds
to user input and interaction.

Which are the advantages of using MVC Framework?
MVC is one of the most used architecture pattern in ASP.NET and this is one of those ASP.NET interview
question to test that do you really understand the importance of model view controller.
It provides a clean separation of concerns between UI and model.
1. UI can be unit test thus automating UI testing.
2. Better reuse of views and model. You can have multiple views which can point to the same

model and also vice versa.
3. Code is better organized.

What is Razor View Engine?
Razor view engine is a new view engine created with ASP.Net MVC model using specially designed Razor
parser to render the HTML out of dynamic server side code. It allows us to write Compact, Expressive,
Clean and Fluid code with new syntaxes to include server side code in to HTML.

What is namespace of asp.net MVC?
ASP.NET MVC namespaces and classes are located in the System.Web.Mvc assembly.
System.Web.Mvc namespace
Contains classes and interfaces that support the MVC pattern for ASP.NET Web applications. This
namespace includes classes that represent controllers, controller factories, action results, views, partial
views, and model binders.
System.Web.Mvc.Ajax namespace
Contains classes that support Ajax scripts in an ASP.NET MVC application. The namespace includes
support for Ajax scripts and Ajax option settings.
System.Web.Mvc.Async namespace
Contains classes and interfaces that support asynchronous actions in an ASP.NET MVC application

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System.Web.Mvc.Html namespace
Contains classes that help render HTML controls in an MVC application. The namespace includes classes
that support forms, input controls, links, partial views, and validation.

How to identify AJAX request with C# in MVC.NET?

The solution is in depended from MVC.NET framework and universal across server-side technologies.
Most modern AJAX applications utilize XmlHTTPRequest to send async request to the server. Such
requests will have distinct request header:
X-Requested-With = XMLHTTPREQUEST


MVC.NET provides helper function to check for Ajax requests which internally inspects X-Requested-
With request header to set IsAjax flag.
HelperPage.IsAjax Property
Gets a value that indicates whether Ajax is being used during the request of the Web page.

Namespace: System.Web.WebPages
Assembly: System.Web.WebPages.dll
However, same can be achieved by checking requests header directly:
Request["X-Requested-With"] == “XmlHttpRequest”

What is Repository Pattern in ASP.NET MVC?
Repository pattern is useful for decoupling entity operations form presentation, which allows easy
mocking and unit testing.
“The Repository will delegate to the appropriate infrastructure services to get the job done.
Encapsulating in the mechanisms of storage, retrieval and query is the most basic feature of a Repository
implementation”
“Most common queries should also be hard coded to the Repositories as methods.”





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.Net Interview Questions
2011
Which MVC.NET to implement repository pattern Controller would have 2 constructors on
parameterless for framework to call, and the second one which takes repository as an input:
class myController: Controller
{
private IMyRepository repository;

// overloaded constructor
public myController(IMyRepository repository)
{
this.repository = repository;
}

// default constructor for framework to call
public myController()
{
//concreate implementation
myController(new someRepository());
}


public ActionResult Load()
{
// loading data from repository
var myData = repository.Load();
}
}

What is difference between MVC (Model-View-Controller) and MVP(Model-View-Presenter)?
The main difference between the two is how the manager (controller/presenter) sits in the overall
architecture.
All requests go first to the Controller
MVC pattern puts the controller as the main ‘guy’ in charge for running the show. All application request
comes through straight to the controller, and it will decide what to do with the request.

Giving this level of authority to the controller isn’t an easy task in most cases. Users interaction in an
application happen most of the time on the View.

Thus to adopt MVC pattern in a web application, for example, the url need to become a way of
instantiating a specific controller, rather than ‘simply’ finding the right View (webform/ html page) to
render out. Every requests need to trigger the instantiation of a controller which will eventually produce
a response to the user.

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This is the reason why it’s alot more difficult to implement pure MVC using Asp.Net Webform. The Url
routing system in Asp.Net webform by default is tied in to the server filesystem or IIS virtual directory
structure. Each of these aspx files are essentially Views which will always get called and instantiated first
before any other classes in the project. (Of course I’m overgeneralizing here. Classes like IHttpModule,
IHttpHandler and Global.asax would be instantiated first before the aspx web form pages).

MVP (Supervising Controller) on the other hand, doesn’t mind for the View to take on a bigger role.
View is the first object instantiated in the execution pipeline, which then responsible for passing any
events that happens on itself to the Presenter.

The presenter then fetch the Models, and pass it back to the view for rendering.

What is the ‘page lifecycle’ of an ASP.NET MVC?
Following process are performed by ASP.Net MVC page:
1) App initialization
2) Routing
3) Instantiate and execute controller
4) Locate and invoke controller action
5) Instantiate and render view

How to call javascript function on the change of Dropdown List in ASP.NET MVC?
Create a java-script function:
<script type="text/javascript">
function selectedIndexChanged() {
}
</script>

Call the function:
<%:Html.DropDownListFor(x => x.SelectedProduct,
new SelectList(Model.Products, "Value", "Text"),
"Please Select a product", new { id = "dropDown1",
onchange="selectedIndexChanged()" })%>

How route table is created in ASP.NET MVC?
When an MVC application first starts, the Application_Start() method is called. This method, in turn, calls
the RegisterRoutes() method. The RegisterRoutes() method creates the route table.

How do you avoid XSS Vulnerabilities in ASP.NET MVC?
Use the syntax in ASP.NET MVC instead of using in .net framework 4.0.

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Explain how to access Viewstate values of this page in the next page?
PreviousPage property is set to the page property of the nest page to access the viewstate value of the
page in the next page.
Page poster = this.PreviousPage;

Once that is done, a control can be found from the previous page and its state can be read.
Label posterLabel = poster.findControl("myLabel");
string lbl = posterLabel.Text;

What is difference between Viewbag and Viewdata in ASP.NET MVC?

The basic difference between ViewData and ViewBag is that in ViewData instead creating dynamic
properties we use properties of Model to transport the Model data in View and in ViewBag we can
create dynamic properties without using Model data.

What is Routing?
A route is a URL pattern that is mapped to a handler. The handler can be a physical file, such as an .aspx
file in a Web Forms application. Routing module is responsible for mapping incoming browser requests
to particular MVC controller actions.

Is it possible to combine ASP.NET webforms and ASP.MVC and develop a single web application?
Yes, it is possible to combine ASP.NET webforms and ASP.MVC and develop a single web application.

Is it possible to unit test an MVC application without running the controllers in an ASP.NET process?
Yes, all the features in an asp.net MVC application are interface based and hence mocking is much
easier. So, we don't have to run the controllers in an ASP.NET process for unit testing.

Is it possible to share a view across multiple controllers?
Yes, put the view into the shared folder. This will automatically make the view available across multiple
controllers.

What is the role of a controller in an MVC application?
The controller responds to user interactions, with the application, by selecting the action method to
execute and also selecting the view to render.

Where are the routing rules defined in an asp.net MVC application?
In Application_Start event in Global.asax





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.Net Interview Questions
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Name a few different return types of a controller action method?
The following are just a few return types of a controller action method. In general an action method can
return an instance of a any class that derives from ActionResult class.
1. ViewResult
2. JavaScriptResult
3. RedirectResult

4. ContentResult
5. JsonResult

What is the significance of NonActionAttribute?
In general, all public methods of a controller class are treated as action methods. If you want prevent
this default behavior, just decorate the public method with NonActionAttribute.

What is the significance of ASP.NET routing?
ASP.NET MVC uses ASP.NET routing, to map incoming browser requests to controller action methods.
ASP.NET Routing makes use of route table. Route table is created when your web application first starts.
The route table is present in the Global.asax file.

What are the 3 segments of the default route, that is present in an ASP.NET MVC application?
1st Segment - Controller Name
2nd Segment - Action Method Name
3rd Segment - Parameter that is passed to the action method

Example:
Controller Name = Article
Action Method Name = id
Parameter Id = 5

ASP.NET MVC application makes use of settings at 2 places for routing to work correctly. What are these
2 places?
1. Web.Config File: ASP.NET routing has to be enabled here.
2. Global.asax File: The Route table is created in the application Start event handler, of the
Global.asax file.

What is the advantage of using ASP.NET routing?
In an ASP.NET web application that does not make use of routing, an incoming browser request should

map to a physical file. If the file does not exist, we get page not found error.

An ASP.NET web application that does make use of routing makes use of URLs that do not have to map
to specific files in a Web site. Because the URL does not have to map to a file, you can use URLs that are
descriptive of the user's action and therefore are more easily understood by users.

P a g e | 20
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What are the 3 things that are needed to specify a route?
1. URL Pattern - You can include placeholders in a URL pattern so that variable data can be passed
to the request handler without requiring a query string.
2. Handler - The handler can be a physical file such as an .aspx file or a controller class.
3. Name for the Route - Name is optional.

Is the following route definition a valid route definition?
{controller}{action}/{id}
No, the above definition is not a valid route definition, because there is no literal value or delimiter
between the placeholders. Therefore, routing cannot determine where to separate the value for the
controller placeholder from the value for the action placeholder.

What is the use of the following default route?
{resource}.axd/{*pathInfo}
This route definition, prevent requests for the Web resource files such as WebResource.axd or
ScriptResource.axd from being passed to a controller.

What is the difference between adding routes, to a webforms application and to an MVC application?
To add routes to a webforms application, we use MapPageRoute() method of the RouteCollection class,

where as to add routes to an MVC application we use MapRoute() method.

How do you handle variable number of segments in a route definition?
Use a route with a catch-all parameter. An example is shown below. * is referred to as catch-all
parameter.
controller/{action}/{*parametervalues}

What are the 2 ways of adding constraints to a route?
1. Use regular expressions
2. Use an object that implements IRouteConstraint interface

Give 2 examples for scenarios when routing is not applied?
1. A Physical File is found that Matches the URL Pattern - This default behavior can be overridden
by setting the RouteExistingFiles property of the RouteCollection object to true.
2. Routing Is Explicitly Disabled for a URL Pattern - Use the RouteCollection.Ignore() method to
prevent routing from handling certain requests.

What is the use of action filters in an MVC application?
Action Filters allow us to add pre-action and post-action behavior to controller action methods.




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If I have multiple filters implanted, what is the order in which these filters get executed?
 Authorization filters

 Action filters
 Response filters
 Exception filters

Give an example for Authorization filters in an asp.net MVC application?
 RequireHttpsAttribute
 AuthorizeAttribute

Which filter executes first in an asp.net MVC application?
Authorization filter

What are the levels at which filters can be applied in an asp.net MVC application?
 Action Method
 Controller
 Application

Is it possible to create a custom filter?
Yes

What filters are executed in the end?
Exception Filters

Is it possible to cancel filter execution?
Yes

What type of filter does OutputCacheAttribute class represents?
Result Filter

What are the 2 popular asp.net MVC view engines?
1. Razor

2. .aspx

What symbol would you use to denote, the start of a code block in razor views?
@

What symbol would you use to denote, the start of a code block in aspx views?
<%= %>

In razor syntax, what is the escape sequence character for @ symbol?

P a g e | 22
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.Net Interview Questions
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The escape sequence character for @ symbol, is another @ symbol

When using razor views, do you have to take any special steps to protect your asp.net MVC application
from cross site scripting (XSS) attacks?
No, by default content emitted using a @ block is automatically HTML encoded to protect from cross
site scripting (XSS) attacks.

When using aspx view engine, to have a consistent look and feel, across all pages of the application, we
can make use of asp.net master pages. What is asp.net master pages equivalent, when using razor
views?
To have a consistent look and feel when using razor views, we can make use of layout pages. Layout
pages, reside in the shared folder, and are named as _Layout.cshtml

What are sections?
Layout pages, can define sections, which can then be overridden by specific views making use of the

layout. Defining and overriding sections is optional.

What are the file extensions for razor views?
 .cshtml - If the programming language is C#
 .vbhtml - If the programming language is VB

How do you specify comments using razor syntax?
Razor syntax makes use of @* to indicate the beginning of a comment and *@ to indicate the end. An
example is shown below.
@* This is a Comment *@

















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.Net Interview Questions
2011
Design Pattern

Command
Encapsulate a request as an object, thereby letting you parameterize clients with different requests,
queue or log requests, and support undoable operations.
/*the Command interface*/

public

interface
Command {

void
execute();
}


/*the Invoker class*/

import
java.util.List;
import
java.util.ArrayList;

public

class

Switch
{


private
List<Command> history =
new
ArrayList<Command>();


public

Switch
() {
}


public

void
storeAndExecute(Command cmd) {

this
.history.add(cmd);
// optional

cmd.execute();
}

}

/*the Receiver class*/

public

class
Light {


public
Light() {
}


public

void
turnOn() {
System.out.println("The light is on");
}


public

void
turnOff() {
System.out.println("The light is off");
}

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}


/*the Command for turning on the light - ConcreteCommand #1*/

public

class
FlipUpCommand
implements
Command {


private
Light theLight;


public
FlipUpCommand(Light light) {

this
.theLight = light;
}

public

void
execute(){
theLight.turnOn();
}

}


/*the Command for turning off the light - ConcreteCommand #2*/

public

class
FlipDownCommand
implements
Command {


private
Light theLight;


public
FlipDownCommand(Light light) {

this
.theLight = light;

}


public

void
execute() {
theLight.turnOff();
}

}


/*The test class or client*/

public

class
PressSwitch {


public

static

void
main(String[] args){
Light lamp =
new
Light();

Command switchUp =
new
FlipUpCommand(lamp);
Command switchDown =
new
FlipDownCommand(lamp);


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.Net Interview Questions
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Switch
s =
new

Switch
();


try
{

if
(args[0].equalsIgnoreCase("ON")) {
s.storeAndExecute(switchUp);
System.exit(0);
}

if
(args[0].equalsIgnoreCase("OFF")) {
s.storeAndExecute(switchDown);
System.exit(0);
}
System.out.println("Argument
\"
ON
\"
or
\"
OFF
\"
is required.");
}
catch
(Exception e) {
System.out.println("Argument's required.");
}
}

}

Iterator
Provide a way to access the elements of an aggregate object sequentially without exposing its
underlying representation.

Null object
Avoid null references by providing a default object.

/* Null Object Pattern implementation:
*/

using
System;

// Animal interface is the key to compatibility for Animal implementations
below.

interface
IAnimal
{

void
MakeSound();
}

// Dog is a real animal.

class
Dog : IAnimal
{

public

void
MakeSound()
{
Console.WriteLine("Woof!");
}

}