Friday, 13 December 2019

ASP.Net MVC Interview questions

                      ASP.Net MVC Interview questions


1) What is MVC?
MVC is a pattern which is used to split the application's implementation logic into three components: models, views, and controllers.


2) Can you explain Model, Controller and View in MVC?
  • Model – It’s a business entity and it is used to represent the application data.
  • Controller – Request sent by the user always scatters through controller and it’s responsibility is to redirect to the specific view using View() method.
  • View – It’s the presentation layer of MVC.
3) Explain the new features added in version 4 of MVC (MVC4)?
Following are features added newly –
  • Mobile templates
  • Added ASP.NET Web API template for creating REST based services.
  • Asynchronous controller task support.
  • Bundling the java scripts.
  • Segregating the configs for MVC routing, Web API, Bundle etc.
4) Can you explain the page life cycle of MVC?
Below are the processed followed in the sequence -
  • App initialization 
  • Routing 
  • Instantiate and execute controller 
  • Locate and invoke controller action 
  • Instantiate and render view.
5) What are the advantages of MVC over ASP.NET?
  • Provides a clean separation of concerns among UI (Presentation layer), model (Transfer objects/Domain Objects/Entities) and Business Logic (Controller). 
  • Easy to UNIT Test. 
  • Improved reusability of model and views. We can have multiple views which can point to the same model and vice versa. 
  • Improved structuring of the code.
6) What is Separation of Concerns in ASP.NET MVC?
It’s is the process of breaking the program into various distinct features which overlaps in functionality as little as possible. MVC pattern concerns on separating the content from presentation and data-processing from content.


7) What is Razor View Engine?
Razor is the first major update to render HTML in MVC 3. Razor was designed specifically for view engine syntax. Main focus of this would be to simplify and code-focused templating for HTML generation. Below is the sample of using Razor:
@model MvcMusicStore.Models.Customer
@{ViewBag.Title = "Get Customers";}
<div class="cust"> <h3><em>@Model.CustomerName</em> </h3>

8) What is the meaning of Unobtrusive JavaScript?
This is a general term that conveys a general philosophy, similar to the term REST (Representational State Transfer). Unobtrusive JavaScript doesn't intermix JavaScript code in your page markup.
Eg : Instead of using events like onclick and onsubmit, the unobtrusive JavaScript attaches to elements by their ID or class based on the HTML5 data- attributes.


9) What is the use of ViewModel in MVC?
ViewModel is a plain class with properties, which is used to bind it to strongly typed view. ViewModel can have the validation rules defined for its properties using data annotations.

10) What you mean by Routing in MVC?
Routing is a pattern matching mechanism of incoming requests to the URL patterns which are registered in route table. Class – “UrlRoutingModule” is used for the same process.

11) What are Actions in MVC?
Actions are the methods in Controller class which is responsible for returning the view or json data. Action will mainly have return type – “ActionResult” and it will be invoked from method – “InvokeAction()” called by controller.

12) What is Attribute Routing in MVC?
ASP.NET Web API supports this type routing. This is introduced in MVC5. In this type of routing, attributes are being used to define the routes. This type of routing gives more control over classic URI Routing. Attribute Routing can be defined at controller level or at Action level like –
[Route(“{action = TestCategoryList}”)] - Controller Level
[Route(“customers/{TestCategoryId:int:min(10)}”)] - Action Level

13) How to enable Attribute Routing?
Just add the method – “MapMvcAttributeRoutes()” to enable attribute routing as shown below
public static void RegistearRoutes(RouteCollection routes) 
{ 
routes.IgnoareRoute("{resource}.axd/{*pathInfo}"); 

//enabling attribute routing 
routes.MapMvcAttributeRoutes();
//convention-based routing 
routes.MapRoute
( 
name: "Default", 
url: "{controller}/{action}/{id}", 
defaults: new { controller = "Customer", action = "GetCustomerList", id = UrlParameter.Optional }
);
}

14) Explain JSON Binding?
JavaScript Object Notation (JSON) binding support started from MVC3 onwards via the new JsonValueProviderFactory, which allows the action methods to accept and model-bind data in JSON format. This is useful in Ajax scenarios like client templates and data binding that need to post data back to the server.

15) Explain Dependency Resolution?
Dependency Resolver again has been introduced in MVC3 and it is greatly simplified the use of dependency injection in your applications. This turn to be easier and useful for decoupling the application components and making them easier to test and more configurable.

16) Explain Bundle.Config in MVC4?
"BundleConfig.cs" in MVC4 is used to register the bundles by the bundling and minification system. Many bundles are added by default including jQuery libraries like - jquery.validate, Modernizr, and default CSS references.

17) How route table has been created in ASP.NET MVC?
Method – “RegisterRoutes()” is used for registering the routes which will be added in “Application_Start()” method of global.asax file, which is fired when the application is loaded or started.

18) Which are the important namespaces used in MVC?
Below are the important namespaces used in MVC -
System.Web.Mvc
System.Web.Mvc.Ajax
System.Web.Mvc.Html
System.Web.Mvc.Async

19) What is ViewData?
Viewdata contains the key, value pairs as dictionary and this is derived from class – “ViewDataDictionary“. In action method we are setting the value for viewdata and in view the value will be fetched by typecasting.

20) What is the difference between ViewBag and ViewData in MVC?
ViewBag is a wrapper around ViewData, which allows to create dynamic properties. Advantage of viewbag over viewdata will be –
  • In ViewBag no need to typecast the objects as in ViewData.
  • ViewBag will take advantage of dynamic keyword which is introduced in version 4.0. But before using ViewBag we have to keep in mind that ViewBag is slower than ViewData.
21) Explain TempData in MVC?
TempData is again a key, value pair as ViewData. This is derived from “TempDataDictionary” class. TempData is used when the data is to be used in two consecutive requests, this could be between the actions or between the controllers. This requires typecasting in view.


22) What are HTML Helpers in MVC?
  • HTML Helpers are like controls in traditional web forms. But HTML helpers are more lightweight compared to web controls as it does not hold viewstate and events.
  • HTML Helpers returns the HTML string which can be directly rendered to HTML page. Custom HTML Helpers also can be created by overriding “HtmlHelper” class.
23) What are AJAX Helpers in MVC?
AJAX Helpers are used to create AJAX enabled elements like as Ajax enabled forms and links which performs the request asynchronously and these are extension methods of AJAXHelper class which exists in namespace - System.Web.Mvc.


24) What are the options can be configured in AJAX helpers?
Below are the options in AJAX helpers –
  • Url – This is the request URL.
  • Confirm – This is used to specify the message which is to be displayed in confirm box. 
  • OnBegin – Javascript method name to be given here and this will be called before the AJAX request.
  • OnComplete – Javascript method name to be given here and this will be called at the end of AJAX request.
  • OnSuccess - Javascript method name to be given here and this will be called when AJAX request is successful.
  • OnFailure - Javascript method name to be given here and this will be called when AJAX request is failed.
  • UpdateTargetId – Target element which is populated from the action returning HTML.
25) What is Layout in MVC?
Layout pages are similar to master pages in traditional web forms. This is used to set the common look across multiple pages. In each child page we can find – /p>
@{ 
Layout = "~/Views/Shared/TestLayout1.cshtml"; 
}
This indicates child page uses TestLayout page as it’s master page.

26) Explain Sections is MVC?
Section are the part of HTML which is to be rendered in layout page. In Layout page we will use the below syntax for rendering the HTML –
@RenderSection("TestSection")
And in child pages we are defining these sections as shown below –
@section TestSection{
<h1>Test Content</h1> 
}
If any child page does not have this section defined then error will be thrown so to avoid that we can render the HTML like this –
@RenderSection("TestSection", required: false)

27) Can you explain RenderBody and RenderPage in MVC?
RenderBody is like ContentPlaceHolder in web forms. This will exist in layout page and it will render the child pages/views. Layout page will have only one RenderBody() method. RenderPage also exists in Layout page and multiple RenderPage() can be there in Layout page.

28) What is ViewStart Page in MVC?
This page is used to make sure common layout page will be used for multiple views. Code written in this file will be executed first when application is being loaded.

29) Explain the methods used to render the views in MVC?
Below are the methods used to render the views from action -
  • View() – To return the view from action.
  • PartialView() – To return the partial view from action.
  • RedirectToAction() – To Redirect to different action which can be in same controller or in different controller.
  • Redirect() – Similar to “Response.Redirect()” in webforms, used to redirect to specified URL.
  • RedirectToRoute() – Redirect to action from the specified URL but URL in the route table has been matched.
30) What are the sub types of ActionResult?
ActionResult is used to represent the action method result. Below are the subtypes of ActionResult –
  • ViewResult
  • PartialViewResult
  • RedirectToRouteResult
  • RedirectResult
  • JavascriptResult
  • JSONResult
  • FileResult
  • HTTPStatusCodeResult
31) What are Non Action methods in MVC?
In MVC all public methods have been treated as Actions. So if you are creating a method and if you do not want to use it as an action method then the method has to be decorated with “NonAction” attribute as shown below –
[NonAction] 
public void TestMethod() 
{ 
// Method logic 
}

32) How to change the action name in MVC?
ActionName” attribute can be used for changing the action name. Below is the sample code snippet to demonstrate more –
[ActionName("TestActionNew")] 
public ActionResult TestAction() 
{ 
return View(); 
}
So in the above code snippet “TestAction” is the original action name and in “ActionName” attribute, name - “TestActionNew” is given. So the caller of this action method will use the name “TestActionNew” to call this action.

33) What are Code Blocks in Views?
Unlike code expressions that are evaluated and sent to the response, it is the blocks of code that are executed. This is useful for declaring variables which we may be required to be used later.
@{ 
 int x = 123; 
 string y = "aa"; 
 }

34) What is the "HelperPage.IsAjax" Property?
The HelperPage.IsAjax property gets a value that indicates whether Ajax is being used during the request of the Web page.

35) How we can call a JavaScript function on the change of a Dropdown List in MVC?
Create a JavaScript method:
<script type="text/javascript"> 
function DrpIndexChanged() { }
</script>
Invoke the method: 
<%:Html.DropDownListFor(x => x.SelectedProduct, new SelectList(Model.Customers, "Value", "Text"), "Please Select a Customer", new { id = "ddlCustomers", onchange=" DrpIndexChanged ()" })%>

36) What are Validation Annotations?
Data annotations are attributes which can be found in the "System.ComponentModel.DataAnnotations" namespace. These attributes will be used for server-side validation and client-side validation is also supported. Four attributes - Required, String Length, Regular Expression and Range are used to cover the common validation scenarios.

37) Why to use Html.Partial in MVC?
This method is used to render the specified partial view as an HTML string. This method does not depend on any action methods. We can use this like below –
@Html.Partial("TestPartialView")

38) What is Html.RenderPartial?
Result of the method – “RenderPartial” is directly written to the HTML response. This method does not return anything (void). This method also does not depend on action methods. RenderPartial() method calls “Write()” internally and we have to make sure that “RenderPartial” method is enclosed in the bracket. Below is the sample code snippet –
@{Html.RenderPartial("TestPartialView"); }

39) What is RouteConfig.cs in MVC 4?
"RouteConfig.cs" holds the routing configuration for MVC. RouteConfig will be initialized on Application_Start event registered in Global.asax.

40) What are Scaffold templates in MVC?
Scaffolding in ASP.NET MVC is used to generate the Controllers,Model and Views for create, read, update, and delete (CRUD) functionality in an application. The scaffolding will be knowing the naming conventions used for models and controllers and views.


41) Explain the types of Scaffoldings.
Below are the types of scaffoldings –
  • Empty
  • Create
  • Delete
  • Details
  • Edit
  • List
42) Can a view be shared across multiple controllers? If Yes, How we can do that?
Yes, we can share a view across multiple controllers. We can put the view in the “Shared” folder. When we create a new MVC Project we can see the Layout page will be added in the shared folder, which is because it is used by multiple child pages.


43) What are the components required to create a route in MVC?
  • Name - This is the name of the route.
  • URL Pattern – Placeholders will be given to match the request URL pattern.
  • Defaults –When loading the application which controller, action to be loaded along with the parameter.
44) Why to use “{resource}.axd/{*pathInfo}” in routing in MVC?
Using this default route - {resource}.axd/{*pathInfo}, we can prevent the requests for the web resources files like - WebResource.axd or ScriptResource.axd from passing to a controller.

45) Can we add constraints to the route? If yes, explain how we can do it?
Yes we can add constraints to route in following ways –
  • Using Regular Expressions
  • Using object which implements interface - IRouteConstraint.
46) What are the possible Razor view extensions?
Below are the two types of extensions razor view can have –
  • .cshtml – In C# programming language this extension will be used.
  • .vbhtml - In VB programming language this extension will be used.
47) What is PartialView in MVC?
PartialView is similar to UserControls in traditional web forms. For re-usability purpose partial views are used. Since it’s been shared with multiple views these are kept in shared folder. Partial Views can be rendered in following ways –
  • Html.Partial()
  • Html.RenderPartial()
48) How we can add the CSS in MVC?
Below is the sample code snippet to add css to razor views –
<link rel="StyleSheet" href="/@Href(~Content/Site.css")" type="text/css"/>

49) Can I add MVC Testcases in Visual Studio Express?
No. We cannot add the test cases in Visual Studio Express edition it can be added only in Professional and Ultimate versions of Visual Studio.

50) What is the use .Glimpse in MVC?
Glimpse is an open source tool for debugging the routes in MVC. It is the client side debugger. Glimpse has to be turned on by visiting to local url link -
  • http://localhost:portname//glimpse.axd 
This is a popular and useful tool for debugging which tracks the speed details, url details etc.

51) What is the need of Action Filters in MVC?
Action Filters allow us to execute the code before or after action has been executed. This can be done by decorating the action methods of controls with MVC attributes.

52) Mention some action filters which are used regularly in MVC?
Below are some action filters used –
  • Authentication 
  • Authorization
  • HandleError
  • OutputCache
53) How can we determine action invoked from HTTP GET or HTTP POST?
This can be done in following way –
  • Use class – “HttpRequestBase” and use the method – “HttpMethod” to determine the action request type.
54) In Server how to check whether model has error or not in MVC?
Whenever validation fails it will be tracked in ModelState. By using property – IsValid it can be determined. In Server code, check like this –
if(ModelState.IsValid){
 // No Validation Errors 
}

55) How to make sure Client Validation is enabled in MVC?
In Web.Config there are tags called – “ClientValidationEnabled” and “UnobtrusiveJavaScriptEnabled”. We can set the client side validation just by setting these two tags “true”, then this setting will be applied at the application level.
<add key="ClientValidationEnabled" value="true" /> 
<add key="UnobtrusiveJavaScriptEnabled" value="true" />

56) What are Model Binders in MVC?
For Model Binding we will use class called – “ModelBinders”, which gives access to all the model binders in an application. We can create a custom model binders by inheriting “IModelBinder”.

57) How we can handle the exception at controller level in MVC?
Exception Handling is made simple in MVC and it can be done by just overriding “OnException” and set the result property of the filtercontext object (as shown below) to the view detail, which is to be returned in case of exception.
protected overrides void OnException(ExceptionContext filterContext)
{
}

58) Does Tempdata hold the data for other request in MVC?
If Tempdata is assigned in the current request then it will be available for the current request and the subsequent request and it depends whether data in TempData read or not. If data in Tempdata is read then it would not be available for the subsequent requests.

59) Explain Keep method in Tempdata in MVC?
As explained above in case data in Tempdata has been read in current request only then “Keep” method has been used to make it available for the subsequent request.
@TempData[“TestData”];
TempData.Keep(“TestData”);

60) Explain Peek method in Tempdata in MVC?
Similar to Keep method we have one more method called “Peek” which is used for the same purpose. This method used to read data in Tempdata and it maintains the data for subsequent request.
string A4str = TempData.Peek("TT").ToString();

61) What is Area in MVC?
Area is used to store the details of the modules of our project. This is really helpful for big applications, where controllers, views and models are all in main controller, view and model folders and it is very difficult to manage.


62) How we can register the Area in MVC?
When we have created an area make sure this will be registered in “Application_Start” event in Global.asax. Below is the code snippet where area registration is done –
protected void Application_Start() 
{ 
AreaRegistration.RegisterAllAreas(); 
}

63) What are child actions in MVC?
To create reusable widgets child actions are used and this will be embedded into the parent views. In MVC Partial views are used to have reusability in the application. Child action mainly returns the partial views.


64) How we can invoke child actions in MVC?
ChildActionOnly” attribute is decorated over action methods to indicate that action method is a child action. Below is the code snippet used to denote the child action –
[ChildActionOnly] 
public ActionResult MenuBar() 
{ 
//Logic here 
return PartialView(); 
}

65) What is Dependency Injection in MVC?
It’s a design pattern and is used for developing loosely couple code. This is greatly used in the software projects. This will reduce the coding in case of changes on project design so this is vastly used.

66) Explain the advantages of Dependency Injection (DI) in MVC?
Below are the advantages of DI –
  • Reduces class coupling 
  • Increases code reusing 
  • Improves code maintainability 
  • Improves application testing
67) Explain Test Driven Development (TDD) ?
TDD is a methodology which says, write your tests first before you write your code. In TDD, tests drive your application design and development cycles. You do not do the check-in of your code into source control until all of your unit tests pass.

68) Explain the tools used for unit testing in MVC?
Below are the tools used for unit testing –
  • NUnit
  • xUnit.NET
  • Ninject 2
  • Moq
69) What is Representational State Transfer (REST) mean?
REST is an architectural style which uses HTTP protocol methods like GET, POST, PUT, and DELETE to access the data. MVC works in this style. In MVC 4 there is a support for Web API which uses to build the service using HTTP verbs.

70) How to use Jquery Plugins in MVC validation?
We can use dataannotations for validation in MVC. If we want to use validation during runtime using Jquery then we can use Jquery plugins for validation.
Eg: If validation is to be done on customer name textbox then we can do as –
$('#CustomerName').rules("add", {
required: true,
minlength: 2,
messages: {
required: "Please enter name",
minlength: "Minimum length is 2"
}
});

71) How we can multiple submit buttons in MVC?
Below is the scenario and the solution to solve multiple submit buttons issue.
Scenario –
@using (Html.BeginForm(“MyTestAction”,”MyTestController”)
{
<input type="submit" value="MySave" />
<input type="submit" value="MyEdit" />


}
Solution :
Public ActionResult MyTestAction(string submit) //submit will have value either “MySave” or “MyEdit”
{
// Write code here
}


72) What are the differences between Partial View and Display Template and Edit Templates in MVC?
  • Display Templates – These are model centric. Meaning it depends on the properties of the view model used. It uses convention that will only display like divs or labels.
  • Edit Templates – These are also model centric but will have editable controls like Textboxes.
  • Partial View – These are view centric. These will differ from templates by the way they render the properties (Id’s) Eg : CategoryViewModel has Product class property then it will be rendered as Model.Product.ProductName but in case of templates if we CategoryViewModel has List<Product> then @Html.DisplayFor(m => m.Products) works and it renders the template for each item of this list.
73) Can I set the unlimited length for “maxJsonLength” property in config?
No. We can’t set unlimited length for property maxJsonLength. Default value is - 102400 and maximum value what we can set would be – 2147483644.

74) Can I use Razor code in Javascript in MVC?
Yes. We can use the razor code in javascript in cshtml by using <text> element.
<script type="text/javascript">
@foreach (var item in Model) {
<text>
//javascript goes here which uses the server values
</text>
}
</script>

75) How can I return string result from Action in MVC?
Below is the code snippet to return string from action method –
public ActionResult TestAction() {
return Content("Hello Test !!");
}

76) How to return the JSON from action method in MVC?
Below is the code snippet to return string from action method –
public ActionResult TestAction() {
return JSON(new { prop1 = “Test1”, prop2 = “Test2” });
}

77) How we can override the action names in MVC?
If we want to override the action names we can do like this –
[ActionName("NewActionName")]
public ActionResult TestAction() {
return View();
}

WCF Interview questions

                                      WCF Interview Questions

1) What is WCF ?
Microsoft has introduced WCF for inter process communication. WCF let us to establish communication channels using MSMQ, Remoting etc.

2) Explain the components used in WCF?
Below are the essential components of WCF –
  • Service class
  • End point
  • Hosting Environment
3) How WCF works?
WCF will follow – “Software and Service Model” , in which all essential components are defined as services and this will be used by client program.



4) Explain the difference between classic web services (ASMX) and WCF?
Classic webservice known as ASMX were using SOAP protocol for sending and receiving the messages over network and over HTTP protocol whereas WCF allows the communication to happen over any transport protocol.




5) What is Endpoint in WCF?
Endpoint will have following properties –
  • Address
  • Binding
  • Contract
6) Explain “Address” property of endpoint in WCF?
Address” property is the part of endpoint defined in service level and this property is used to determine the location if the service, where it is located.

7) Explain “Binding” property of endpoint in WCF?
Binding” property is the part of endpoint defined in service level and this property is used to decide out the type protocols, encoding's and transport. These all factors has been decided by both the parties who want to communicate each other.

8) Explain “Contract” property of endpoint in WCF?
It is just an interface between client and server where client and server communicate each other. Contracts are used to identify operations available.

9) Explain the types of contracts available in WCF?
Below are the list types of contracts available in WCF
  • Data Contracts
  • Service Contracts
  • Message Contracts
  • Fault Contracts
10) Explain “Service Contracts” in WCF?
Service Contracts attribute given at the service level for WCF service and it will give you the list of operations that can be performed from that service. Service Contracts can be defined like –
[ServiceContract]


11) Mention the list of bindings supported by WCF?
Below are the list of schemas supported by WCF –
  • TCP
  • HTTP
  • MSMQ
  • IPC
  • Peer Network
12) Explain the ways to host the WCF Service?
Below are ways to host WCF Service –
  • IIS
  • Self Hosting
  • WAS
13) What is the Address format in WCF?
Below is the syntax of address –
[transport]://[machine or domain][optional port number]


14) What are duplex contracts in WCF?
Duplex contracts mainly uses duplex messaging which is used for callback to the client. Duplex messaging uses transport systems like – HTTP, TCP or Named Pipe.

15) What are different instance modes in WCF?
Below are the list of instance modes in WCF –
  • Per Call
  • Singleton
  • Per Session
16) Explain “Per Call” instance mode in WCF?
In “Per Call” mode, When a request has made to service, new instance of service will be created for each method call and this will be disposed once the response goes to client.



17) Explain “Per Session” instance mode in WCF?
Per Session” creates a logical session between service and client and it will be maintained till the session the ends. When client requests from service the session will be created and it is dedicated to instance for that client and it will going to end when client session ends.




18) Explain “Singleton” instance mode in WCF?
In “Singleton” mode all the clients are connected to the single instance of the service and when service configured for “Singleton” mode, instance will be created when service is hosted and it will be disposed once its shuts down.

19) What is Throttling in WCF?
Throttling” is used to limit the sessions or instances to be created at application level. And this will increase the performance.
20) What is the significance of “maxConcurrentCalls” in Throttling?
This attribute in throttling is used to limit the total number of calls which are going to the service instances. The default value is 16.

21) What is Service Proxy in WCF?

WCF Proxies are used to enable the communication between client and server by exchanging the messages in the form of requests and responses. It will have the details like Service Path, Protocol details and so on.

22) Explain Service Oriented Architecture?
Service Oriented Architecture is known as SOA. It is a design pattern where business functionality will be as a service and client will communicate to the service using proxy. Advantage of this will be – It is independent of platforms, vendor and product.

23) Why to use DataContarcts in WCF?
In WCF we can communicate with server from our client through message. So messages will be going to and fro between server and client. For security purpose we are serializing the messages sent across the wire.
[DataContact]” attribute given at class level to serialize the class by using “[Datamember]” attribute over properties.

24) Mention types of transaction managers in WCF?
Below are the types of transaction managers –
  • WS- Atomic Transaction
  • Light Weight
  • OLE Transaction
25) Explain DataContractSerializer ?
DataContractSerializer is introduced in .NET 3.0 and WCF uses DataContractSerializer as default one. But now this serializer can be used for other serialization purposes also. For serialization “WriteObject()” method is used.
Eg: DataContractSerializer dataContractSerializer = new DataContractSerializer(typeof(MyTestClassType));

26) Explain XMLSerializer ?
This serializer was there from the beginning of .NET version. To serialize or deserialize an object just create an instance of XmlSerializer and pass the type of object. Methods – “Serialize()” or “DeSerialize()” methods used to serialize and deserialize objects respectively.
Eg: System.Xml.Serialization.XmlSerializer xmlSerializer = new System.Xml.Serialization.XmlSerializer(typeof(MyTestClassType));

27) What are Operation Contracts in WCF?
Operation Contracts are the contracts between client and server on operations or methods which the service provides to the client. The methods used by the service are to be decorated by “[OperationContract]” attribute.

28) What are different modes of communication in WCF?
Below are the list of modes of communication between server and client –
  • One-Way
  • Request-Reply
  • Callback
29) Explain “Request-Reply” mode in WCF?
By default WCF works in this mode. When client made a request to a service, client will wait till it gets the response back to the client. If the response is not received till the given time, timeout error thrown. If client gets the response then next instructions will be executed.

30) What is the significance of “receiveTimeout” property in WCF?
This property is used to get/set the time interval that a connection remains active.


31) Explain “One-Way” mode in WCF?
In this mode client send a request to the server but does not wait till the response comes and does not care whether the request is failed or succeeded. Client will not blocked in this case till it receives the response.



32) Explain “Callback” mode in WCF?
This is the special mode of WCF where WCF on call back calls the method of client and in this scenario WCF service acts like a client and client acts like a service. But “HTTPBinding” does not support this mode we have to switch to “WSDualHttpBinding”.




33) What are Events in WCF?
Events allow the clients to get notified once it’s occurred in service side. Events will always result in direct call from client. Since service firing the event it’s called the publisher and since client is being notified about the event it is called subscriber.

34) What is the namespace used for WCF?
Namespace “System.ServiceModel” is used for WCF.

35) What are the isolation levels in WCF?
Below are the list of isolation levels in WCF –
  • Read Committed
  • Read Uncommitted
  • Serializable
  • Repeatable Read
36) List out Address format of all the bindings in WCF?
Below are the formats of address and its respective bindings –
  • TCF Address Format - net.tcp://local host:portnumber
  • HTTP Address Format - http://local host:portnumber
  • MSMQ Address Format - net.msmq://local host:portnumber
37) What is WCF RIA?
This is the framework for developing n-tier application for RIA (Rich Internet App). This is used in for Rich Internet Apps like Silverlight, AJAX etc. It solves major problems like – Tight Coupling.

38) How to generate proxy for WCF?
Proxy can generated from below steps –
  • Using Visual Studio
  • Using SvcUtil
39) Explain how to generate proxies using Svcutil in WCF?
SvcUtil is a command line utility. We can write the below command to generate proxy –
svcutil /t:code http://<mycreatedserviceurl>/out:<file_name>.cs /config:<file_name>.config

40) What you mean by “Transport Reliability” ?
Transport Reliability” meaning the guaranteed delivery of packets over network as protocol TCP does. It is not only the guaranteed delivery of packets it maintains the order of the packets as well.

41) What are default endpoints in WCF?
If service does not have any endpoints either in config or in program, by default WCF adds up one endpoint to the service created.

42) How to enable metadata information of the service?
Below are the ways to enable the metadata for WCF –
  • For Default Endpoint - <serviceMetadata> tag is used in web.config file without specifying the endpoint.
  • For Custom Endpoint - - <serviceMetadata> tag is used in web.config file with specifying the defined endpoint.
43) Which bindings are used for metadata configuration in WCF?
Below are the list of bindings that are used for metadata –
  • mexHttpBinding
  • mexNamedPipeBinding
  • mexHttpsBinding
  • mexTcpBinding
44) What is the way to test our WCF application without creating client application?
Tool called - “wcftestclient.exe” used for testing the WCF service without creating a client application. We can open this tool from visual studio command prompt.

45) How to configure the reliability in configs file?
In config file we can use the tag of reliability as in the below code snippet –
<bindings>
 <netTcpBinding>
 <binding name = "MyTestBinding">
 <reliableSession enabled = "true"/>
 </binding>
 </netTcpBinding>
</bindings>

46) Can overload methods in WCF? If Yes, How?
Yes we can overload operations or methods in WCF. Below is the sample code depicts the same –
[ServiceContract]
interface IMyTestCalculator
{
 [OperationContract(Name = "AddTestInteger")]
 int AddTest(int pararm1,int pararm2);
 [OperationContract(Name = "AddTestDouble")]
 double AddTest(double pararm1,double pararm2);
}

47) Explain Known Types in WCF?
If we define the complex complex class as the property of class would give a hard time for the compiler during deserilization process. So we will use attribute - KnownType to the parent class.

48) Give an example for KnownType?
Please check the below example for KnowTypes –
[KnownType(typeof(TestClassCar))]
[KnownType(typeof(TestClassTruck))]
[DataContract]
public class TestClassVehicle 
{
}

[DataContract]
public class TestClassCar : TestClassVehicle
{
}
[DataContract]
public class TestClassTruck : TestClassVehicle
{
}

49) Explain ServiceKnownType in WCF?
ServiceKnownType is used at Opeartion/Method level. When serviceknowntype is applied to the operation then that only operation will use known type.
50) Give an example for ServiceKnownType?
Below is the sample code snippet –
public Interface ITestVehicleService
{
 [ServiceKnownType(typeof(TestClassCar))]
 [ServiceKnownType(typeof(TestClassTruck))]

[OperationContract]
Vehicle AddNewTestVehicle(TestClassVehicle myVehicle);

[OperationContract]
 bool UpdateTestVehicle(TestClassVehicle myTestVehicle); 
}

51) What are Fault Contracts in WCF?
This contract is used to raise the error from service side or in simple words client will come to know about the service error from fault contract.

52) Write a code snippet for Fault Contract in WCF Service?
Below is the code snippet for fault contract –
public Interface ITestVehicleService
{
 [ServiceKnownType(typeof(TestClassCar))]
 [ServiceKnownType(typeof(TestClassTruck))]

[OperationContract]
Vehicle AddNewTestVehicle(TestClassVehicle myVehicle);

[OperationContract]
 [FaultContract(typeof(VehicleFault))]
 bool UpdateTestVehicle(TestClassVehicle myTestVehicle); 
}

[DataContract]
public class VehicleFault
{ 
 private string vehicle;
 private string problemType;

[DataMember]
 public string Vehicle
 {
 get { return vehicle; }
 set { vehicle = value; }
 }

[DataMember] 
 public string ProblemType
 {
 get { return problemType; }
 set { problemType = value; }
 }
}

53) What are Styles of models WCF supports?
WCF service supports 2 styles of models –
  • RPC style - In RPC-style we can use the serialize types and it provides the feature that are available for local calls.
  • Message style - Message style WCF allows the message header to be customized and it also allows us to define the security for body and header messages.
54) What are Message Contracts in WCF?
Message is the data which is passed from client to server and vice versa. WCF mainly uses SOAP protocol for sending these messages to and fro. Message Contract can be applied to the class and “MessageHeader” and “MessageBodyMember” attributes are used for custom body and header included in the message. (class)



55) What are the modes of sessions in WCF?
Below are the list of session modes in WCF –
  • Allowed
  • Required
  • Not Allowed
56) What is Durable Service?
These are WCF services which are used to persist the session state and its information even after client restarted the service host. It may use SQL for data storing state information.




57) How to implement Durable Services?
Durable services use “DurableService” attribute which can have attributes – “CanCreateInstance” and “CompletesInstance”.

58) Can we have two-way binding for MSMQ?
Yes we can have two-way bindings for MSMQ.

59) Explain dead letter queues?
Queue does not need to have a continuous connection between client and server. Message will be in queue once client or server puts some data into that and will stay till it has been picked up by client or server. In case that queue has not been picked within given timestamp then it will expire and is called dead letter queues.

60) How to track the service users?
Using “Parameter Inspector” extension we can track WCF service users. We can use methods like – “AfterCall” and “BeforeCall”.

61) How we can manage session in WCF?
Below are the ways to maintain the session in WCF –
  • Per Call
  • Per Session
  • Single
62) What are the main security features used in WCF?
Below are the features used to address security features –
  • Integrity
  • Confidentiality
  • Authentication
  • Authorization
63) What are the difference between transport level and message level security?
  • Transport Level Security – It happens at channel level. WCF uses transport like – TCP, HTTP, MSMQ etc. and each of these transports have its own security features.
  • Message Level Security – Here security is at the message level, while transferring the data to and from between client and server.
64) What is OData?
OData or Open Data Protocol is used to access the information exposed by data sources like SQL, Cloud Storage etc. using different clients like – browsers, BI, mobile etc.

65) Explain parts on OData?
Below are the main parts of Odata –
  • OData Data Model
  • OData Protocol
  • OData Service
  • OData Client Libraries
66) Can we call WCF service in Jquery?
Yes we can call WCF service in Jquery that is called WCF data service and this can be called from AJAX call.

67) What are transactions?
It is a group of operations which are executed in whole and it provides a way to logically group pieces and execute them at one shot.

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