MVC Interview Questions

1. What are the 3 main components of an ASP.NET MVC application?
1. M - Model
2. V - View
3. C - Controller

2. In which assembly is the MVC framework defined?
System.Web.Mvc

3. 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.

4. 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.

5. 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. Which approach provides better support for test driven development - ASP.NET MVC or ASP.NET Webforms?
ASP.NET MVC

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.

8. 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.

9. 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.

10. 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 alse selecting the view to render.

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

12. 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

13. 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.

14. 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.

15. 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://pragimtech.com/Customer/Details/5
Controller Name = Customer
Action Method Name = Details
Parameter Id = 5

16. 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.

17. 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.

18. 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.

19. 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.

20. 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.

21. 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.

22. 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}

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

24. 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.

25. 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.

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

27. 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

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

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


30. What are the levels at which filters can be applied in an asp.net mvc application?
1. Action Method
2. Controller
3. Application
 
31. Is it possible to create a custom filter?
 Yes

32. What filters are executed in the end?
Exception Filters

33. Is it possible to cancel filter execution?
Yes

34. What type of filter does OutputCacheAttribute class represents?
Result Filter

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

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

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

38. In razor syntax, what is the escape sequence character for @ symbol?
The escape sequence character for @ symbol, is another @ symbol

39. 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.

40. 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

41. 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.

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

43. 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. An example is shown below.
@* This is a Comment *@

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WCF Interview Questions

1. What is the difference between WCF and ASMX Web Services?

Simple and basic difference is that ASMX or ASP.NET web service is designed to send and receive messages using SOAP over HTTP only. While WCF can exchange messages using any format (SOAP is default) over any transport protocol (HTTP, TCP/IP, MSMQ, NamedPipes etc).

2. 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.

[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.

            <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.

             <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:

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

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