MVC3

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.
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 and also 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 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

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 usefult 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.”

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 goes first to the ControllerMVC 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.

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 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 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;

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 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.

wcfInterviewQ

What are WCF Service Endpoints? Explain.

For Windows Communication Foundation services to be consumed, it’s necessary that it must be exposed; Clients need information about service to communicate with it. This is where service endpoints play their role.

A WCF service endpoint has three basic elements i.e. Address, Binding and Contract.

• Address: It defines "WHERE". Address is the URL that identifies the location of the service.
• Binding: It defines "HOW". Binding defines how the service can be accessed.
• Contract: It defines "WHAT". Contract identifies what is exposed by the service.

3. What are the possible ways of hosting a WCF service? Explain.

For a Windows Communication Foundation service to host, we need at least a managed process, a ServiceHost instance and an Endpoint configured. Possible approaches for hosting a service are:

1. Hosting in a Managed Application/ Self Hosting
   1. Console Application
   2. Windows Application
   3. Windows Service
2. Hosting on Web Server
   1. IIS 6.0 (ASP.NET Application supports only HTTP)
   2. Windows Process Activation Service (WAS) i.e. IIS 7.0 supports HTTP, TCP, NamedPipes, MSMQ.

4. How we can achieve Operation Overloading while exposing WCF Services?

By default, WSDL doesn’t support operation overloading. Overloading behavior can be achieved by using "Name" property of OperationContract attribute.

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[ServiceContract]
interface IMyCalculator
{
   [OperationContract(Name = "SumInt")]
   int Sum(int arg1,int arg2);

   [OperationContract(Name = "SumDouble")]
   double Sum(double arg1,double arg2);
}

When the proxy will be generated for these operations, it will have 2 methods with different names i.e. SumInt and SumDouble.

5. What Message Exchange Patterns (MEPs) supported by WCF? Explain each of them briefly.

1. Request/Response 2. One Way 3. Duplex

Request/Response

It’s the default pattern. In this pattern, a response message will always be generated to consumer when the operation is called, even with the void return type. In this scenario, response will have empty SOAP body.

One Way

In some cases, we are interested to send a message to service in order to execute certain business functionality but not interested in receiving anything back. OneWay MEP will work in such scenarios. If we want queued message delivery, OneWay is the only available option.

Duplex

The Duplex MEP is basically a two-way message channel. In some cases, we want to send a message to service to initiate some longer-running processing and require a notification back from service in order to confirm that the requested process has been completed.

6. What is DataContractSerializer and How its different from XmlSerializer?

Serialization is the process of converting an object instance to a portable and transferable format. So, whenever we are talking about web services, serialization is very important.

Windows Communication Foundation has DataContractSerializer that is new in .NET 3.0 and uses opt-in approach as compared to XmlSerializer that uses opt-out. Opt-in means specify whatever we want to serialize while Opt-out means you don’t have to specify each and every property to serialize, specify only those you don’t want to serialize. DataContractSerializer is about 10% faster than XmlSerializer but it has almost no control over how the object will be serialized. If we wanted to have more control over how object should be serialized that XmlSerializer is a better choice.

7. How we can use MessageContract partially with DataContract for a service operation in WCF?

MessageContract must be used all or none. If we are using MessageContract into an operation signature, then we must use MessageContract as the only parameter type and as the return type of the operation.

8. Which standard binding could be used for a service that was designed to replace an existing ASMX web service?

The basicHttpBinding standard binding is designed to expose a service as if it is an ASMX/ASP.NET web service. This will enable us to support existing clients as applications are upgrade to WCF.

9. Please explain briefly different Instance Modes in WCF?

WCF will bind an incoming message request to a particular service instance, so the available modes are:

• Per Call: instance created for each call, most efficient in term of memory but need to maintain session.
• Per Session: Instance created for a complete session of a user. Session is maintained.
• Single: Only one instance created for all clients/users and shared among all.Least efficient in terms of memory.

10. Please explain different modes of security in WCF? Or Explain the difference between Transport and Message Level Security.

In Windows Communication Foundation, we can configure to use security at different levels

a. Transport Level security means providing security at the transport layer itself. When dealing with security at Transport level, we are concerned about integrity, privacy and authentication of message as it travels along the physical wire. It depends on the binding being used that how WCF makes it secure because most of the bindings have built-in security.

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            <netTcpBinding>
            <binding name="netTcpTransportBinding">
               <security mode="Transport">
                          <Transport clientCredentialType="Windows" />
               </security>
            </binding>
            </netTcpBinding>

b. Message Level Security For Tranport level security, we actually ensure the transport that is being used should be secured but in message level security, we actually secure the message. We encrypt the message before transporting it.

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             <wsHttpBinding>
             <binding name="wsHttpMessageBinding">
               <security mode="Message">
                           <Message clientCredentialType="UserName" />
               </security>
              </binding>
             </wsHttpBinding>

It totally depends upon the requirements but we can use a mixed security mode also as follows:

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             <basicHttpBinding>
             <binding name="basicHttp">
               <security mode="TransportWithMessageCredential">
                          <Transport />
                               <Message clientCredentialType="UserName" />
               </security>
             </binding>
             </basicHttpBinding>