Friday, January 11, 2013

MVC asp.net interview question answer




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.
1- In which assembly is the MVC framework defined?
System.Web.Mvc
2- 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.
3- What does Model, View and Controller represent in an MVC application?
Model: Model represents the application data domain. In short the applications business logic is contained with in the model.

View: Views represent the user interface, with which the end users interact. In short the all the user interface logic is contained with in the UI.

Controller: Controller is the component that responds to user actions. Based on the user actions, the respective controller, work with the model, and selects a view to render that displays the user interface. The user input logic is contained with in the controller.
4- What is the greatest advantage of using asp.net mvc over asp.net webforms?
It is difficult to unit test UI with webforms, where views in mvc can be very easily unit tested.
6- 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.
7- What are the advantages of ASP.NET MVC?
1. Extensive support for TDD. With asp.net MVC, views can also be very easily unit tested.
2. Complex applications can be easily managed
3. Seperation of concerns. Different aspects of the application can be divided into Model, View and Controller.
4. ASP.NET MVC views are light weight, as they donot use viewstate.
9- 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
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.
10- 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.

11- 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.

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

13- 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
14- 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
15- 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 behaviour, just decorate the public method with NonActionAttribute.

16- 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.

17- 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.

18- 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: http://google.com/search/label/MVC
Controller Name = search
Action Method Name = label
Parameter Id = MVC
19- 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.
How do you avoid XSS Vulnerabilities in ASP.NET MVC?
Use thesyntax in ASP.NET MVC instead of usingin .net framework 4.0.

20- What is the adavantage 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.

21- 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.

22- 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.

23- 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.

24- 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.

25- 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}

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

27- Give 2 examples for scenarios when routing is not applied?
1. A Physical File is Found that Matches the URL Pattern - This default behaviour can be overriden 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.

28- 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.

29- If I have multiple filters implemented, what is the order in which these filters get executed?
1. Authorization filters
2. Action filters
3. Response filters
4. Exception filters

30- What are the different types of filters, in an asp.net mvc application?
1. Authorization filters
2. Action filters
3. Result filters
4. Exception filters

31- Give an example for Authorization filters in an asp.net mvc application?
1. RequireHttpsAttribute
2. AuthorizeAttribute

32- Which filter executes first in an asp.net mvc application?
Authorization filter

33- What are the levels at which filters can be applied in an asp.net mvc application?
1. Action Method
2. Controller
3. Application

34- Is it possible to create a custom filter?
Yes

35- What filters are executed in the end?
Exception Filters

36- Is it possible to cancel filter execution?
Yes

37- What type of filter does OutputCacheAttribute class represents?
Result Filter

38- What are the 2 popular asp.net mvc view engines?
1. Razor
2. .aspx

39- 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.

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

41- 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?
The escape sequence character for @ symbol, is another @ symbol

42- When using razor views, do you have to take any special steps to proctect 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.

43- 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

44- What are sections?
Layout pages, can define sections, which can then be overriden by specific views making use of the layout. Defining and overriding sections is optional.

45- What are the file extensions for razor views?
1. .cshtml - If the programming lanugaue is C#
2. .vbhtml - If the programming lanugaue is VB

46- How do you specify comments using razor syntax?
Razor syntax makes use of @* to indicate the begining of a comment and *@ to indicate the end.

47- 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.

Thank
RS Prajapati
Sr.Software Engg.
Interactive,India

 

Tuesday, January 8, 2013

DevHelp: Difference between beginexecutereader and execute...

DevHelp: Difference between beginexecutereader and execute...: The BeginExecuteReader(...) and EndExecuteReader...() are for performing the ExecuteReader(...) method asynchronously. If you use Execute...

Some Imp Question



The BeginExecuteReader(...) and EndExecuteReader...() are for performing the
ExecuteReader(...) method asynchronously. If you use ExecuteReader(...)
your thread is blocked while that method executes.

Using BeginExecuteReader(...) (and the corresponding EndExecuteReader(...))
ExecuteReader(...) will be executed in a seperate thread, allowing for
yours to continue processing. The BeginExecuteReader(...) method will
require a callback method, and in that callback method, you will make a
call to EndExecuteReader(...) to end the asynchronous operation, and
retreive the return value.
Correlated subquery
Correlated subquery runs once for each row selected by the outer query. It contains a reference to a value 
 from the row selected by the outer query.
Correlated subquery follows down to top approach i.e., main query is executed first(even though parenthesis       
 are present) and then child query. 
We can also say:In a subquery.
Example:
 select e1.empname, e1.basicsal, e1.deptno from emp e1
 where e1.basicsal = (select max(basicsal) from emp e2 where e2.deptno = e1.deptno)
Nested subquery
Nested subquery runs only once for the entire nesting (outer) query. It does not contain any reference to the 
 outer query row.
We can also say: in a Correlated subquery,Inner query condition is used in the outer query.
Nested subquery follows top-down approach i.e., child query is executed first and then parent .
Outer query condition is used in the the inner query.
Example:
 select empname, basicsal, deptno from emp
 where (deptno, basicsal) in (select deptno, max(basicsal) from emp group by deptno)


Thread

Threads share the address space of the process that created it.
Threads have direct access to the data segment of its process.
Threads can directly communicate with other threads of its process.
Threads have almost no overhead.
New threads are easily created.
Threads can exercise considerable control over threads of the same process
Changes to the main thread (cancellation, priority change, etc.) may affect the behavior of the other threads of the process.

Process

Processes have their own address.
Processes have their own copy of the data segment of the parent process.
Processes must use inter-process communication to communicate with sibling processes.
Processes have considerable overhead.
New processes require duplication of the parent process.
Processes can only exercise control over child processes.
Changes to the parent process does not affect child process.

The BeginExecuteReader(...) and EndExecuteReader...() are for performing the
ExecuteReader(...) method asynchronously. If you use ExecuteReader(...)
your thread is blocked while that method executes.

Using BeginExecuteReader(...) (and the corresponding EndExecuteReader(...))
ExecuteReader(...) will be executed in a seperate thread, allowing for
yours to continue processing. The BeginExecuteReader(...) method will
require a callback method, and in that callback method, you will make a
call to EndExecuteReader(...) to end the asynchronous operation, and
retreive the return value.
Correlated subquery
Correlated subquery runs once for each row selected by the outer query. It contains a reference to a value 
 from the row selected by the outer query.
Correlated subquery follows down to top approach i.e., main query is executed first(even though parenthesis       
 are present) and then child query. 
We can also say:In a subquery.
Example:
 select e1.empname, e1.basicsal, e1.deptno from emp e1
 where e1.basicsal = (select max(basicsal) from emp e2 where e2.deptno = e1.deptno)


Nested subquery
Nested subquery runs only once for the entire nesting (outer) query. It does not contain any reference to the 
 outer query row.
We can also say: in a Correlated subquery,Inner query condition is used in the outer query.
Nested subquery follows top-down approach i.e., child query is executed first and then parent .
Outer query condition is used in the the inner query.
Example:
 select empname, basicsal, deptno from emp
 where (deptno, basicsal) in (select deptno, max(basicsal) from emp group by deptno)

============================================================================
Trace:
This class works only when your application build defines the symbol TRACE.
For tracing, you have to use Trace.WriteLine statements.
Trace class is generally used to trace the execution during deployment of the application.
Trace class works in both debug mode as well as release mode.
Performance analysis can be done using Trace class.
Trace runs in a thread that is different from the Main Thread.
Trace is used during Testing Phase and Optimization Phase of different releases.

Debug:
This class works only when your application build defines the symbol DEBUG.
For debug, you have to use Debug.WriteLine statements.
You generally use debug classes at the time of development of application.
Debug class works only in debug mode.
Performance analysis cannot be done using Debug class.
Debug runs in the same thread in which your code executes.
Debug is used during Debugging Phase.

Web service:
The File extension of web service is .asmx.
It can be hosted in IIS.
[WebService] attribute has to be added to the class.
[WebMethod] attribute represents the method exposed to client.
One-way, Request- Response are the different operations supported in web service.
System.Xml.serialization name space is used for serialization.
XML 1.0, MTOM(
Message Transmission Optimization Mechanism), DIME, Custom.
Hash Table cannot be serialized.
Only public properties/fields can be serialized.
Unhandled Exceptions returns to the client as SOAP faults.
Slower than WCF.
Uses only SOAP(Simple Object Access Protocol).

WCF:
The file extension of WCF service is .svc.
It can be hosted in IIS, windows
 activation service, Self-hosting, Windows service.
[ServiceContraact] attribute has to be added to the class.
[OperationContract] attribute represents the method exposed to client.
One-Way, Request-Response, Duplex are different type of operations supported in WCF.
System.Runtime.Serialization namespace is used for serialization.
XML 1.0, MTOM, Binary, Custom.
The DataContractSerializer translate the
 Hash table into the XML.
Public/
Private properties/fields can be serialized.
Better than WebService. The performance measures in terms of xml serialization.
It can send/receive
 message in any transport protocol message format. By default it uses SOAP for communication.

The WHERE clause selects rows before grouping. The HAVING clause selects rows after grouping.
The WHERE clause cannot contain aggregate functions. The HAVING clause can contain aggregate functions.

A HAVING clause is like a WHERE clause, but applies only to groups as a whole, whereas the WHERE clause applies to
 individual rows. A query can contain both a WHERE clause and a HAVING clause. The WHERE clause is applied first to the individual rows in the tables . Only the rows that meet the conditions in the WHERE clause are grouped. The HAVING clause is then applied to the rows in the result set.

DevHelp

DevHelp

Implementing Service Locator (To Resolve Dependency)

using System; /// <summary> /// Summary description for Class1 /// </summary> public class serviceLocator {     public s...