MVC stands for Model View Controller.
It divides an application into 3 component roles which is based on a framework
methodology.
These component roles are discussed briefly as follows:
i) Models : These component roles are used to maintain the state which is
persisted inside the Database.
Example: we might have a Product class that is used to represent order data
from the Products table inside SQL.
ii) Views : These component roles are used to display the user interface of the
application, where this UI is created off of the model data.
Example: we might create an Product “Edit” view that surfaces textboxes,
dropdowns and checkboxes based on the current state of a Product object.
iii) Controllers : These component roles are used for various purposes like
handling end user interaction, manipulating the model, and ultimately choosing
a view to render to display UI.
Note:
In a MVC application, the views are used only for displaying the information
whereas the controllers are used for handling and responding to user input and
interaction.
The MVC framework is defined through System.Web.Mvc assembly.
This is because this is the only assembly which contains classes and interfaces
that support the ASP.NET Model View Controller (MVC) framework for creating Web
applications.
We can combine ASP.NET MVC into an existing ASP.NET application by following
the below procedure:
First of all, you have to add a reference to the following three assemblies to
your existing ASP.NET application:
i) System.Web.Routing
ii) System.Web.Abstractions
iii) System.Web.Mvc
The ASP.NET MVC folder should be created after adding these assembly
references.
Add the folder Controllers, Views, and Views | Shared to your existing ASP.NET
application.
And then you have to do the necessary changes in web.config file.
For this you can refer to the below link:
http://www.packtpub.com/article/mixing-aspnet-webforms-and-aspnet-mvc
The main advantages of using asp.net mvc are as follows:
i) One of the main advantage is that it will be easier to manage the complexity
as the application is divided into model,view and controller.
ii) It gives us the full control over the behavior of an application as it does
not use view state or server-based forms.
iii) It provides better support for test-driven development (TDD).
iv) You can design the application with a rich routing infrastructure as it
uses a Front Controller pattern that processes Web application requests through
a single controller.
This Razor View engine is a part of new rendering framework for ASP.NET web
pages.
ASP.NET rendering engine uses opening and closing brackets to denote code
(<% %>), whereas Razor allows a cleaner, implied syntax for determining
where code blocks start and end.
Example:
In the classic renderer in ASP.NET:
<ul>
<% foreach (var userTicket in Model)
{ %>
<li><%: userTicket.Value
%></li>
<% } %>
</ul>
By using Razor:
<ul>
@foreach (var userTicket in Model)
{
<li>@userTicket.Value</li>
}
</ul>
In an MVC application, all the features are based on interface. So, it is easy
to unit test a MVC application.
And it is to note that, in MVC application there is no need of running the controllers
for unit testing.
System.Web.Mvc namespace contains all the interfaces and classes which supports
ASP.NET MVC framework for creating web applications.
Yes, It is possible to share a view across multiple controllers by putting a
view into the shared folder.
By doing like this, you can automatically make the view available across
multiple controllers.
A controller will decide what to do and what to display in the view. It works
as follows:
i) A request will be received by the controller
ii) Basing on the request parameters, it will decide the requested activities
iii) Basing on the request parameters, it will delegates the tasks to be
performed
iv) Then it will delegate the next view to be shown
An action method is used to return an instance of any class which is derived
from ActionResult class.
Some of the return types of a controller action method are:
i) ViewResult : It is used to return a webpage from an action method
ii) PartialViewResult : It is used to send a section of a view to be rendered
inside another view.
iii) JavaScriptResult : It is used to return JavaScript code which will be
executed in the user’s browser.
iv) RedirectResult : Based on a URL, It is used to redirect to another
controller and action method.
v) ContentResult : It is an HTTP content type may be of text/plain. It is used
to return a custom content type as a result of the action method.
vi) JsonResult : It is used to return a message which is formatted as JSON.
vii) FileResult : It is used to send binary output as the response.
viii) EmptyResult : It returns nothing as the result.
The page lifecycle of an ASP.NET MVC page is explained as follows:
i) App Initialisation
In this stage, the aplication starts up by running Global.asax’s
Application_Start() method.
In this method, you can add Route objects to the static RouteTable.Routes
collection.
If you’re implementing a custom IControllerFactory, you can set this as the
active controller factory by assigning it to the
System.Web.Mvc.ControllerFactory.Instance property.
ii) Routing
Routing is a stand-alone component that matches incoming requests to
IHttpHandlers by URL pattern.
MvcHandler is, itself, an IHttpHandler, which acts as a kind of proxy to other
IHttpHandlers configured in the Routes table.
iii) Instantiate and Execute Controller
At this stage, the active IControllerFactory supplies an IController instance.
iv) Locate and invoke controller action
At this stage, the controller invokes its relevant action method, which after
further processing, calls RenderView().
v) Instantiate and render view
At this stage, the IViewFactory supplies an IView, which pushes response data
to the IHttpResponse object.
It is already known that all the public methods of a controller class are
basically treated as action methods.
If you dont want this default behaviour, then you can change the public method
with NonActionAttribute. Then, the default behaviour changes.
The Router Table is formed by following the below procedure:
In the begining stage, when the ASP.NET application starts, the method known as
Application_Start() method is called.
The Application_Start() will then calls RegisterRoutes() method.
This RegisterRoutes() method will create the Router table.
There are 3 segments of the default route in an MVC application.They are:
The 1st segment is the Controller Name.
Example: search
The 2nd segment is the Action Method Name.
Example: label
The 3rd segment is the Parameter passed to the Action method.
Example: Parameter Id - MVC
The settings must be done in 2 places for the routing to work properly.They
are:
i) Web.Config File : In the web.config file, the ASP.NET routing has to be
enabled.
ii) Global.asax File : The Route table is created in the application Start
event handler, of the Global.asax file.
To avoid xss vulnerabilities, you have to use the syntax as '<%: %>' in
ASP.NET MVC instead of using the syntax as '<%= %>' in .net framework
4.0.
This is because it does the HTML encoding.
Example:
<input
type="text" value="<%: value%>" />
Without using Routing in an ASP.NET MVC application, the incoming browser
request should be mapped to a physical file.The thing is that if the file is
not there, then you will get a page not found error.
By using Routing, it will make use of URLs where there is no need of mapping to
specific files in a web site.
This is because, for the URL, there is no need 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.
There are 3 things that are required to specify a route.
i) URL Pattern : You can pass the variable data to the request handler without
using a query string. This is done by including placeholders in a URL pattern.
ii) Handler : This handler can be a physical file of 2 types such as a .aspx
file or a controller class.
iii) Name for the Route : This name is an optional thing.
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{controller}{action}/{id} is not a valid route definition.
The reason is that, it has no literal value or delimiter between the
placeholders.
If there is no literal, the routing cannot determine where to seperate the
value for the controller placceholder from the value for the action
placeholder.
With the help of this default route {resource}.axd/{*pathInfo}, you can prevent
requests for the web resources files such as WebResource.axd or
ScriptResource.axd from being passed to a controller.
We use MapPageRoute() method of a RouteCollection class for adding routes to a
webforms application, whereas MapRoute() method is used to add routes to an MVC
application.
You can handle variable number of segments in a route definition by using a
route with a catch-all parameter.
Example:
controller/{action}/{*parametervalues}
Here * reffers to catch-all parameter.
There are 2 ways for adding constraints to a route. They are:
i) By using Regular Expressions and
ii) By using an object which implements IRouteConstraint interface.
Below are the 2 scenarios where routing is not applied.
i) 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.
ii) Routing Is Explicitly Disabled for a URL Pattern - By using the
RouteCollection.Ignore() method, you can prevent routing from handling certain
requests.
Action filter in an mvc application is used to perform some additional
processing, such as providing extra data to the action method, inspecting the
return value, or canceling execution of the action method.
Action filter is an attribute that implements the abstract FilterAttribute
class.
As there are different types of filters in an MVC application, the
Authorization filter is the one which executes first and Exeption filters
executes in the end.
Both are used to pass the data from controllers to views.
The difference between Viewbag and Viewdata in ASP.NET MVC is explained below:
View Data:
In this, objects are accessible using strings as keys.
Example:
In the Controller:
public ActionResult Index()
{
var softwareDevelopers = new List<string>
{
"Brendan Enrick",
"Kevin Kuebler",
"Todd Ropog"
};
ViewData["softwareDevelopers"] = softwareDevelopers;
return View();
}
In the View:
<ul>
@foreach (var developer in
(List<string>)ViewData["softwareDevelopers"])
{
<li>
@developer
</li>
}
</ul>
An important note is that when we go to use out object on the view that we have
to cast it since the ViewData is storing everything as object.
View Bag:
It will allow the objectto dynamically have the properties add to it.
Example:
In the Controller:
public ActionResult Index()
{
var softwareDevelopers = new List<string>
{
"Brendan Enrick",
"Kevin Kuebler",
"Todd Ropog"
};
ViewBag.softwareDevelopers = softwareDevelopers;
return View();
}
In the View:
<ul>
@foreach (var developer in ViewBag.softwareDevelopers)
{
<li>
@developer
</li>
}
</ul>
An important point to note is that there is no need to cast our object when
using the ViewBag. This is because the dynamic we used lets us know the type.
There are two types of file extensions for razor views.
They are:
i) .cshtml : This file extension is used, when the programming language is a
C#.
ii) .vbhtml : This file extension is used, when the programming language is a
VB.
In razor syntax, we use the below shown symbols for specifying comments.
i) For indicating the begining of a comment, we use @* syntax.
ii) For indicating the end of a comment, we use *@ syntax.
In ASP.NET MVC, validation helpers are used to show the validation error
messages in a view.
The Html.ValidationMessage() and Html.ValidationSummary() helpers are used in
the automatically generated Edit and Create views by the ASP.NET MVC.
To create a view, the following steps are to be followed:
i) In the product controller,right click on the Create() action and then select
the option Add View.
ii) Now check the checkbox labeled in the Add View dialog and create a
strongly-typed view.
iii) Select the product class from the View data class dropdownlist.
iv) Now, select Create from the view content dropdownlist.
v) Finally, click on the Add button.
No, It is not possible to create a MVC Unit Test application in Visual Studio
Standard.
It is also not possible to create in Visual Studio Express.
It is possible to create only in Visual Studio Professional and Visual Studio
Enterprise Versions.
It is an Open Source platform for gathers and presents detailed diagnostic
information about the execution of your web application.It tells you exactly what's
going on with each request.
We used in a similar manner to client side diagnostics and debugging tools like
FireBug or Chrome Developer Tools.
It is used to reveal what is happening within your ASP.NET MVC and WebForms
sites.
By default, visual studio doesn't provide Jquery intellisense support, but it
can be achieved by adding vsdoc.js file to razor view.
@if(false)
{
<script src="~/script/jquery-1.7.1-vsdoc.js"
type="text/javascript"></script>
}
No te : If statement prevents the rendering of script tag
into the Html source code and it used only by visual studio for Jquery
intellisense support.
1. Asp.net Webform follows an event-driven development
model whereas Asp.net Mvc follow Model, View, Controller design pattern.
2. Asp.net Webform has server controls whereas Asp.net
Mvc has Html helpers for creating UI of application.
3.Asp.net Webforms
has state management techniques whereas Asp.net Mvc doesn't have automatic
state management techniques.
4. Asp.net Webform has file- based Urls means file name
exists in Url whereas Asp.net Mvc has route-based Url.
5. In Asp.net webform, webforms(Aspx) are tightly coupled
to code-behind (Aspx.cs) whereas in Asp.net Mvc, Views and logic are kept
separately.
6. Asp.net Webform has Master page for consistent look
and feel whereas in Asp.net Mvc layout is for this.
7. Asp.net Webform has User Controls for code
re-usability whereas in Asp.net Mvc partial view is for this.
A partial view is like as user control in Asp.Net web form. Partial views are
reusable views like as Header and Footer. It has .csHtml extension.
Partial and RenderPartial Html method renders partial view in Mvc razor.
<div>@Html.Partial("_Comments")</div>
<div>@ { Html.RenderPartial("_Comments") } </div>
Strongly type view is used for rendering specific type of model object. By
specifying the type of data we get intellisense for that model class. View
inherits from Viewpage whereas strongly typed view inherits from
Viewpage<T> where T is type of the model.
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@using(Html.Beginform())
{
Content Here.....
}
It ensures that an object is disposed when it goes out of scope.
Add stylesheet :
<link rel="StyleSheet"
href="@Href(~Content/Site.css")" type="text/css"/>
It is a tool that provides flexible menus, breadcrumb trails, and SEO features
for the .NET MVC framework, similar to the ASP.NET SiteMapProvider model.
You can download it as free through NuGet package for .NET MVC 2.0/3.0/4.0
Cross Site Request Forgery (CSRF) is a type of attack on the web application or
on the website where a malicious user can insert or update data on behalf of
the logged in user of the application by giving him a link that is not of the
victim website but attackers own website.
In this type of attack the victim website user doesn't know that by clicking on
malicious user link he is helping him to update malicious data into his
website.
This generally happen by posting data on the victim website by a hidden form
and submitting in using JavaScript or jQuery automatically.
To avoid Cross Site Request Forgery (CSRF) in ASP.NET MVC, you need to do two
things.
1. Add [ValidateAntiForgeryTocken] attribute in
the Controller Action method which is executing when the form data is being
submitted.
2. Add @Html.AntiForgeryTocken() element in the
HTML form.
There are 6 different types of Scaffold templates in ASP.NET MVC that is used
to create a view automatically based on the Model selected.
Empty:
It creates an empty view and only model type is specified in the View page using
@model
Create:
It creates a view with a form that helps to create a new record for the model.
It automatically generates a label and input field for each property in the
Model.
Delete :
It creates a view with the list of records from the Model collection along with
Delete link to delete records.
Details:
It creates a view that displays a lable and the value of each property of the
Model.
Edit
It creates a view with a form for editing existing model data. It also
generates a form with label and field for each property of the Model.
List:
It creates a view with html table that lists the model from the Model
collection. It generates html table column for each property of the model. In
general, it accepts IEnumerable<ModelType> and iterate through each item
of the Enumerable collection. It automatically renders edit, delete links for
each record of the Model collection in a column and Create link on the page
that target to Create action.
In the default template of ASP.NET MVC, we get _ViewStart.cshtml page that is
used to almost similar to MasterPage in ASP.NET Web Form or like a layout
template.
The code of ViewStart executes before the actual view code executes. By
default, _ViewStart template is applied to all view files of this or any sub
directory under this directory.
The _ViewStart.cshtml file contains following code.
@{
Layout = "~/Views/Shared/_Layout.cshtml";
}
As this code runs before any view code so we have flexibility to specify a
different Layout for a particular view.
Because this code runs before any view, a view can override the Layout property
and choose a different
one.
To write dashed attribute of HTML element using ASP.NET MVC Helper methods, we
replace "-" with "_" in the anonymous type parameter. eg.
@using
(Html.BeginForm("Create", "Home", FormMethod.Post,
new { data_validatable=true }))
returns below output
<form action="/Home/Create"
method="Post" data-validatable="true"
>
Notice, the data-validate attribute of the form element.
The Html.ValidationSummary helper method is used to display all validation
errors in the ModelState dictionary, either model property level or errors
associated with ModelState.
Model Property level errors are errors that
are set as an attributes of the property of the Model. eg
[Required]
[StringLength(100, ErrorMessage="The Title must not be more than 100
characters long.")]
public string Title { get; set; }
In the above code, the Title field is a mandatory field and can only accept 100
characters.
The ModelState level errors are errors that
are set by developer in the Controller by using below code snippet.
ModelState.AddModelError("",
"There is an error!");
In this case, the error will be displayed in place of Validation summary like
this
<div
class="validation-summary-errors">
<ul>
<li>There is an error!</li>
</ul>
</div>
The attribute in the Model field for the Identity column of the database should
be
DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)
like below
[Key]
[DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)]
[Required]
public int CategoryId { get; set; }
Thanks
MVC is a framework pattern that splits an application logic into three
different roles: Model, View and Controller.
Model: Business entity on which overall application
operates.MVC does not specifically mention the Data access layer as it is
encapsulated by the model.
View: User interface that renders the model into a form of
interaction.
Controller: Handles the request from the view and updates the
model resulting in a change in model's state.
These are the three important classes(model, view and controller) required for
MVC architecture.
The process of breaking a computer program into various features that overlap
in functionality implies Separation of concerns.
MVC separates the content from presentation and data-processing from content.
For group of views that all use the same layout, this can get a bit redundant
and harder to maintain.
The _ViewStart.cshtml page can be used to remove this redundancy. The code
within this file
is executed before the code in any view placed in the same directory. This fi
le is also recursively applied to any view within a subdirectory.
When we create a default ASP.NET MVC project, we find there is already a
_ViewStart
.cshtml fi le in the Views directory. It specifi es a default layout:
@{
Layout = "~/Views/Shared/_Layout.cshtml";
}
Because this code runs before any view, a view can override the Layout property
and choose a different one. If a set of views shares common settings, the
_ViewStart.cshtml file is a useful place to consolidate these common view
settings. If any view needs to override any of the common settings, the view
can set those values to another value.
The controller gets the first hit and loads the model. Most of the time we
would like to pass the model to the view for displaying data and so we use
session variables, viewstate and so on. But the problem with using sessions or
view state object is the scope. ASP.NET sessions have session scope and the
view state have page scope. In MVC, we would like the data to be maintained
when the hit comes to the controller and reaches the view and after that the
scope of the data should expire.
That’s where the new session management technique has been introduced in the
ASP.NET MVC framework, i.e., ViewData.
[HttpPost]
public ActionResult SaveResumeAsPdf(FormCollection fc)
{
if (Session["UserName"] != null)
{
BaseFont font = BaseFont.CreateFont(BaseFont.COURIER, BaseFont.CP1250, false);
PdfContentByte _pcb;
Document document = new Document();
try
{
PdfWriter writer = PdfWriter.GetInstance(document, new
FileStream(Server.MapPath("~/Resumes/" +
Session["UserName"] + ".pdf"), FileMode.Create));
document.Open();
_pcb = writer.DirectContent;
_pcb.BeginText();
_pcb.SetFontAndSize(font, 14);
int count = 30;
foreach (string item in fc.AllKeys)
{
_pcb.ShowTextAligned(PdfContentByte.ALIGN_LEFT, item, 50, 780 - count, 0);
_pcb.ShowTextAligned(PdfContentByte.ALIGN_LEFT, fc[item], 250, 780 - count, 0);
count = count + 30;
}
_pcb.EndText();
writer.Flush();
}
finally
{
document.Close();
}
}
}
Whenever you want to use two models in a single view, then add the models to
the view in the following way,
@using MvcSampleCFA_02032014.Models;
@model Tuple<PersonCFA, AddressCFA>
Now, you can access all the properties present in the two models.
Repositories are minly used in MVC. It does not mean creating the database by
itself or storing the data anywhere. It is just an approach in MVC. As we have
n-tier architecture in asp.net, similarly repositories are a kind of
architecture in MVC where we can create a repository class and write all the
business logic in this class. We can just call this method from controller and
there is no need to write any kind of business logic which makes our controller
simple.
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Normally, I would put most of general layout related css into content/style.css
If you use theme, then put it into content/theme/{themename}/style.css
If you create custom html control, i would try to create another css file for
control and put it under content/control.css
In most of time, jquery is used in the asp.net MVC, so it make sense to put
it's css in Script/jquery/{pluginName}/xxx.css
There could be more, but that's what's in my head now.
Splitting the css into multiple files is a good thing from a maintenace point
of view. It makes it easier to work with and apply changes. However, multiple
files can have an impact on application performance as the browser has to
download each file individually. You can haev the best of both worlds though.
The technique that is recommended is to bundle all your html files for
deployment so that it is served as 1 single file. The nice thing about this
approach is that it lets you develop with multiple files, giving you ease of
use. But get on the fly css file combination so that your browser only has to
download one file.
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Url.RouteUrl is used to generate a fully qualified URL for
specified route values by using a route name configured in
App_Start/RouteConfig.cs file.
@Url.RouteUrl("MyCustomRoute",
new { action = "New", id = 12, Name = "Sheo" })
gives output as
/CustomController/New/12?Name=Sheo
Url.HttpRouteUrl is also used to generate fully qualified URL for the specified
route values but for Web API Routes. Internally this method add an
"httproute" entry to routeValues. GetVirtualPath method of the Web
Api route classes return null unless we include "httproute" in the
values.
@Url.HttpRouteUrl("MyCustomRoute",
new { action = "New", id = 12, Name = "Sheo" })</p>
gives output as
/CustomController/New/12?Name=Sheo&httproute=True.
Notice httproute query-string at the end.
Its not mandatory to be URL string must be in controller/action/params format.
If User defined in his RouteConfig file like {controller}/{action}/{id} Query string
will be controller/action/id.
if user defined in his RouteConfig file like {action}/{controller}/{id} Query string
will be
Action/controlleer/id.
Html.EditorFor
@Html.EditorFor(model
=> model.LastName)
This HTML helper method is very dynamic in nature. Based on which type of data
is passed to this method, the output changes.
For example,
1. if model property type is of string type, it renders a textbox
2. if the property type is boolean type it renders a checkbox.
3. if the property type is of integer type, it render input
type="number" textbox.
In order to control the output of the Html.EditorFor we can use EditorTemplates
for different data types.
Html.TextBoxFor
@Html.TextBoxFor(model
=> model.LastName)
This HTML helper method only renders a TextBox as output irrespective of
whatever data type the model property is of.
No,we do not have ViewState concept in Asp.Net MVC that is used for storing or
persisting the values of controls in the current page.
So,Asp.Net MVC pages are very Lightweighted and our request and response times
becomes much faster.
1. For retaining the values during postback in the MVC
page values we can use Ajax,so that values in the control will never be clear.
2. For temporarily storing the value in current and the
subsequent requests,we can use TempData concept.
