Wednesday, July 25, 2012

MVC3 QAs


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 Productclass 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 MVCapplication the view is only about displaying information – it is the controller that handles and responds touser 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 interviewquestion to test that do you really understand the importance of model view controller.1. It provides a clean separation of concerns between UI and model.2. UI can be unit test thus automating UI testing.3. Better reuse of views and model. You can have multiple views which can point to the same model andalso vice versa.4. 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 designedRazor 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. Thisnamespace includes classes that represent controllers, controller factories, action results, views, partialviews, and model binders.
System.Web.Mvc.Ajax namespace
Contains classes that support Ajax scripts in an ASP.NET MVC application. The namespace includessupport 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 includesclasses 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. Suchrequests will have distinct request header:
X-Requested-With = XMLHTTPREQUEST
MVC.NET provides helper function to check for ajax requests which internally inspects X-Requested-Withrequest 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.dllHowever, 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 usefult for decoupling entity operations form presentation, which allows easymocking and unit testing.“The Repository will delegate to the appropriate infrastructure services to get the job done. Encapsulatingin the mechanisms of storage, retrieval and query is the most basic feature of a Repositoryimplementation”“Most common queries should also be hard coded to the Repositories as methods.”
 
Which MVC.NET to implement repository pattern Controller would have 2 constructors on parameterlessfor 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 overallarchitecture.
All requests goes first to the Controller
MVC pattern puts the controller as the main ‘guy’ in charge for running the show. All application requestcomes 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 anapplication 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 instantiatinga specific controller, rather than ‘simply’ finding the right View (webform/ html page) to render out. Everyrequests need to trigger the instantiation of a controller which will eventually produce a response to theuser.This is the reason why it’s alot more difficult to implement pure
MVC using Asp.Net Webform. The Urlrouting system in Asp.Net webform by default is tied in to the server filesystem or IIS virtual directorystructure. Each of these aspx files are essentially Views which will always get called and instantiated firstbefore 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 isthe first object instantiated in the execution pipeline, which then responsible for passing any events thathappens 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:
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, callsthe RegisterRoutes() method. The RegisterRoutes() method creates the route table.
 
How do you avoid XSS Vulnerabilities in ASP.NET MVC?
Use thesyntax in ASP.NET MVC instead of usingin .net framework 4.0.
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 thepage 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;
How to create dynamic property with the help of viewbag in ASP.NET MVC?
PreviousPage property is set to the page property of the nest page to access the viewstate value of thepage 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 dynamicproperties we use properties of Model to transport the Model data in View and in ViewBag we can createdynamic 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 .aspxfile in a Web Forms application. Routing module is responsible for mapping incoming browser requests toparticular MVC controller actions

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