MVC Interview Question in Dotnet
1. What is MVC ?
MVC is an architectural pattern
which separates the representation and user interaction.
M - Model - Application business logic is in the Model
V - View - Views represent the user
interface, with which the end users interact.
C - 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.
2.
Advantages of MVC
1.
ASP.NET MVC views are light weight, as they do not use
viewstate.
2.
Extensive support for TDD. With asp.net MVC, views can
also be very easily unit tested.
3.
Complex application can be easily managed by the
developer.
4.
In Razor view engine using a @ block is automatically
HTML encoded to protect from cross site scripting (XSS) attacks.
5.
Bundling and minification improves load time by
reducing the number of requests to the server and reducing the size of
requested assets (such as CSS and JavaScript.). Bundling that makes it easy to
combine or bundle multiple files into a single file.
6.
Minification performs a variety of different code
optimizations to scripts or css, such as removing unnecessary whitespace and
comments and shortening variable names to one character.
3. MVC
Application Life cycle
MVC application life cycle has two
main phases
Creating the request object and
sending our response to the browser.
Creating the
request Object
Step 1: Fill
route : - MVC requests are mapped to route tables which in turn specify
which controller and action to be invoked. So if the request is the first
request the first thing is to fill the route table with routes collection. This
filling of route table happens in the global.asax file.
Step 2: Depending on
the URL sent “UrlRoutingModule” searches the route table to create “RouteData” object which has the
details of which controller and action to invoke.
Step 3 Request
context created: - The “RouteData” object is used to create the
“RequestContext” object.
Step 4 Controller
instance created: - This request object is sent to “MvcHandler” instance to
create the controller class instance. Once the controller class object is
created it calls the “Execute” method of the controller class.
Creating
Response object: - This phase has two steps executing the action and finally
sending the response as a result to the view.
4.Routing in
MVC
Routing is a pattern matching system that monitor the
incoming request and figure out what to do with that request. At runtime,
Routing engine use the Route table for matching the incoming request's URL
pattern against the URL patterns defined in the Route table. You can register
one or more URL patterns to the Route table at Application_Start event.
routes.MapRoute(
"View", // Route name
"View/ViewCustomer/{id}", // URL with parameters
new { controller = "Customer", action = "DisplayCustomer",
id = UrlParameter.Optional }); // Parameter defaults
"View", // Route name
"View/ViewCustomer/{id}", // URL with parameters
new { controller = "Customer", action = "DisplayCustomer",
id = UrlParameter.Optional }); // Parameter defaults
The route mapping code is written in
"RouteConfig.cs" file and registered using "global.asax" application
start event.
5.HTML helpers in MVC
HTML helpers help you to render HTML controls in the view.
For instance if you want to display a HTML textbox on the view , below is the
HTML helper code.
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<%= Html.TextBox("LastName") %>
6. Difference between
HTML.TextBoxFor and HTML.TextBox
Both of them provide the same HTML output, “HTML.TextBoxFor”
is strongly typed while “HTML.TextBox” isn’t
Html.TextBox("CustomerCode")
Html.TextBoxFor(m => m.CustomerCode)
7.Attribute based routing in
MVC
This is a feature introduced in MVC 5. By using the
"Route" attribute we can define the URL structure.
public class HomeController : Controller
{
[Route("Users/about")]
public ActionResult GotoAbout()
{
return View();
}
}
{
[Route("Users/about")]
public ActionResult GotoAbout()
{
return View();
}
}
Most of the time developers code in the action methods.
Developers can see the URL structure right upfront rather than going to the
“routeconfig.cs” and see the lengthy codes.
8. Navigate from one view to
another using a hyperlink?
<%= Html.ActionLink("Home","Gotohome")
%>
Home - Controller
Gotohome - Action
9. Restrict MVC actions to be
invoked only by GET or POST
We can decorate the MVC action with the HttpGet or HttpPost
attribute to restrict the type of HTTP calls. For instance you can see in the
below code snippet the DisplayCustomer action can only be invoked by HttpGet.
If we try to make HTTP POST on DisplayCustomer, it will throw an error.
[HttpGet]
public ViewResult DisplayCustomer(int id)
{
Customer objCustomer = Customers[id];
return View("DisplayCustomer",objCustomer);
}
public ViewResult DisplayCustomer(int id)
{
Customer objCustomer = Customers[id];
return View("DisplayCustomer",objCustomer);
}
10.ViewData, ViewBag and
TempData
ASP.NET MVC offers us three options ViewData, ViewBag and
TempData for passing data from controller to view and in next request. ViewData
and ViewBag are almost similar and TempData performs additional responsibility.
Helps to maintain data when you move from controller to view.
ViewData requires typecasting for complex data type and check
for null values to avoid error and ViewBag doesn’t require typecasting for
complex data type.
ViewBag & ViewData
Example:
public ActionResult Index()
{
ViewBag.Name
= "Arun Prakash";
return
View();
}
public ActionResult Index()
{
ViewData["Name"]
= "Arun Prakash";
return
View();
}
In View, we call like below:
@ViewBag.Name
@ViewData["Name"]
TempData:
Helps to maintain data when you move from one controller to
another controller or from one action to other action. In other words when you
redirect, “Tempdata” helps to maintain data between those redirects. It
internally uses session variables. TempData is meant to be a very short-lived
instance, and you should only use it during the current and the subsequent
requests only.
It requires typecasting for complex data type and check for
null values to avoid error.
So if “TempData” is once read it will not be available in the
subsequent request.
11.Partial views in MVC?
Partial view is a reusable view (like a user control) which
can be embedded inside other view.
12.Validations in MVC?
Data annotations are nothing but attributes which can be
applied on model properties.
Types
[Required]
[StringLength(50, MinimumLength = 2)]
[Range(15, 100)]
Data type
The data type annotation can be used to specify the data type
for validation. The information may also be used as UI hint later in rendering
process.
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[Url]
public string url { get; set; }
[Phone]
public string phone { get; set; }
[DataType(DataType.Date)]
public DateTime updatedate { get; set; }
[DataType(DataType.PhoneNumber)]
public string phone { get; set; }
public class Customer
{
[Required(ErrorMessage="Customer code is required")]
public string CustomerCode
{
set;
get;
}
}
{
[Required(ErrorMessage="Customer code is required")]
public string CustomerCode
{
set;
get;
}
}
<% using (Html.BeginForm("PostCustomer",
"Home", FormMethod.Post))
{ %>
<%=Html.TextBoxFor(m => m.CustomerCode)%>
<%=Html.ValidationMessageFor(m => m.CustomerCode)%>
<%}%>
{ %>
<%=Html.TextBoxFor(m => m.CustomerCode)%>
<%=Html.ValidationMessageFor(m => m.CustomerCode)%>
<%}%>
Later in the controller we can check if the model is proper
or not by using the ModelState.IsValid property and accordingly we can take
actions.
public ActionResult PostCustomer(Customer obj)
{
if (ModelState.IsValid)
{
obj.Save();
return View("Thanks");
}
else
{
return View("Customer");
}
}
{
if (ModelState.IsValid)
{
obj.Save();
return View("Thanks");
}
else
{
return View("Customer");
}
}
13.Can we display all errors
in one go?
Yes, we can; use the ValidationSummary method from the Html
helper class.
<%= Html.ValidationSummary() %>
14. Ajax in MVC
Implement Ajax using Ajax
libraries
function GetData()
{
var url
= "/MyAjax/getCustomer";
$.post(url,
function (data)
{
$("#txtCustomerCode").val(data.CustomerCode);
$("#txtCustomerName").val(data.CustomerName);
}
)
}
implement AJAX by using the
“AJAX” helper library
<%
var AjaxOpt = new
AjaxOptions{OnSuccess="OnSuccess"};
%>
<% using
(Ajax.BeginForm("getCustomer","MyAjax",AjaxOpt)) { %>
<%} %>
15.Difference between
ActionResult and ViewResult?
ActionResult is an abstract class while ViewResult derives
from the ActionResult class.
ActionResult has several derived classes like ViewResult,
JsonResult, FileStreamResult, and so on.
Depending on the flag (IsHtmlView) it will either return a
ViewResult or JsonResult.
public ActionResult DynamicView()
{
if (IsHtmlView)
return View(); // returns simple
ViewResult
else
return Json(); // returns
JsonResult view
}
16.Different types of results
in MVC?
There 12 kinds of results in MVC, at the top is the
ActionResult class which is a base class that can have 11 subtypes as listed
below:
1.ViewResult
- Renders a specified view to the response stream
2.PartialViewResult
- Renders a specified partial view to the response stream
3.EmptyResult
- An empty response is returned
4.RedirectResult
- Performs an HTTP redirection to a specified URL
5.RedirectToRouteResult
- Performs an HTTP redirection to a URL that is determined by the routing
engine, based on given route data
6.JsonResult
- Serializes a given ViewData object to JSON format
7.JavaScriptResult
- Returns a piece of JavaScript code that can be executed on the client
8.ContentResult
- Writes content to the response stream without requiring a view
9.FileContentResult
- Returns a file to the client
10.FileStreamResult
- Returns a file to the client, which is provided by a Stream
11.FilePathResult
- Returns a file to the client
17. Areas in MVC?
Group the controller
classes into logical section
18. MVC Scaffolding
Scaffolding is a technique in which the MVC template helps to
auto-generate CRUD code. CRUD stands for create, read, update and delete.
19.Multiple Submit buttons
pointing to multiple actions in a single MVC view
HTML Way
Ajax Way
20. MVC Ajax Example
//MVC JQuery Ajax
$('#learnitem-form').ajaxSubmit({
data : {
data1: data1,
data2: data2,
},
success :
function(result){
//success
},
error : function(){
//error
}
});
20. MVC Action Filters
ASP.NET MVC provides Action Filters for executing filtering
logic either before or after an action method is called. Action Filters are
custom attributes that provide declarative means to add pre-action and
post-action behavior to the controller's action methods.
Authorization filter, which
makes security decisions about whether to execute an action method, such as
performing authentication or validating properties of the request.
Action filter, which
wraps the action method execution. This filter can perform additional
processing, such as providing extra data to the action method, inspecting the
return value, or canceling execution of the action method
OnActionExecuting - Runs before
execution of Action method.
OnActionExecuted - Runs after
execution of Action method.
OnResultExecuting - Runs before
content is rendered to View.
OnResultExecuted - Runs after
content is rendered to view.
Result filter, which
wraps execution of the ActionResult object. This filter can perform additional
processing of the result, such as modifying the HTTP response.
Exception filter, which
executes if there is an unhandled exception thrown somewhere in action method,
starting with the authorization filters and ending with the execution of the
result. Exception filters can be used for tasks such as logging or displaying
an error page.
21. MVC Custom Filters
When you request any page into MVC Application, it will go
through the Routing Architecture. Your Routing system will decide your URL
pattern. The default routing algorithm is like {controller}/ {action}/ {id}
patterns. But it can be possible to change that pattern using Custom Routes.
When you create a Custom Route, you can also include route
constraints. These constraints are used to restrict the requests to match
routes. There are three basic types of constraints:
1. Regular Expression Constraints - check the
pattern of the Route and prevent invalid requests
2. HttpMethod Constraints - You can
match route with any type of the HTTP operation like POST, GET, etc. you want
to prevent user to access particular URL when GET operation occurs but not POST
operation occurs.
//Custom Route With HttpMethod
Constraint
routes.MapRoute(
"HttpMethodConstraintRoute",
"Blog/Insert",
new { Controller =
"Blog", action = "Insert" },
new { method = new
HttpMethodConstraint("GET") });
3. CatchAllRoutes- Suitable for
the dynamic URL, But if you want to match your URL, regardless of the
number of the segments for that, we
have to create Catch-All Parameter.
22.Action Results - ActionResult
method works as a return type of any controller method in the MVC. It acts like
the base class of Result classes. It is used to return the models to the Views,
file streams and also redirect to the controllers.
23.Razor View Engine VS Web
Form(ASPX) View Engine
1.
Razor Engine is an advanced view engine that was
introduced with MVC3.
Web Form Engine is the default view
engine for the Asp.net MVC that is included with Asp.net MVC from the
beginning.
2. The
file extensions used with Razor Engine are different from Web Form Engine. It
has .cshtml (Razor
with
C#) or .vbhtml (Razor with VB) extension for views, partial views,
editor templates and for layout pages.
3. The file extensions used with
Web Form Engine are also like Asp.net Web Forms. It has .aspx extension for
views, .ascx extension for partial views & editor templates and
.master extension for layout/master pages.
4. Razor
has new and advance syntax that are compact, expressive and reduces typing.
Web Form
Engine has the same syntax like Asp.net Web Forms uses for .aspx pages.
5. Razor syntax are easy to learn
and much clean than Web Form syntax. Razor uses @ symbol to make the code like
as:
@Html.ActionLink("SignUp",
"SignUp")
Web Form syntax are borrowed from
Asp.net Web Forms syntax that are mixed with html and sometimes make a view
messy. Webform uses <% and %> delimiters to make the code like as:
<%:
Html.ActionLink("SignUp", "SignUp") %>
6.By default, Razor Engine prevents
XSS attacks(Cross-Site Scripting Attacks) means it encodes the script or html
tags like <,> before rendering to view.
Web Form Engine does not prevent
XSS attacks means any script saved in the database will be fired while
rendering the page
7. Razor Engine is little bit slow
as compared to Webform Engine.
Web Form Engine is faster than
Razor Engine.
8. Razor Engine, doesn't support
design mode in visual studio means you cannot see your page look and feel.
Web Form engine support design mode
in visual studio means you can see your page look and feel without running the
application.
9. Razor Engine support TDD (Test
Driven Development) since it is not depend on System.Web.UI.Page class.
Web Form Engine doesn't support TDD
(Test Driven Development) since it depend on System.Web.UI.Page class which
makes the testing complex.
