Asp.Net MVC Intro

Asp.Net MVC
A new “pluggable” web framework
Stefano Paluello
[email protected]
http://stefanopaluello.wordpress.com
Twitter: @palutz

MVC and Asp.Net
The Model, the View and the Controller (looks like “The Good, the Bad and the Ugly” )
HtmlHelper and PartialView
Routing
Filters
TDD with Asp.Net MVC
Agenda

MVC and Asp.Net
From WebForm to MVC

Asp.Net
Asp.Net was introduced in 2002 (.Net 1.0)
It was a big improvement from the “spaghetti code” that came with Asp classic
It introduced a new programming model, based on Events, Server-side Controls and “stateful” Form (Session, Cache, ViewState): the RAD/VB-like development model for the web.
It allowed a lot of developers to deal with the Web, also if they have limited or no skills at all in HTML and JavaScript.
Build with productivity in mind

Windows Form and Web Form models
Server
Reaction
Code
Action
Server
HttpRequest
Serialize/
Deserialize
Webform state
Code
HttpResponse

Events and State management are not HTTP concepts (you need a quite big structure to manage them)
The page life cycle, with all the events handler, can become really complicated and also delicate (easy to break)
You have low control over the HTML code generated
The complex Unique ID values for the server-side controls don’t fit well with Javascript functions
There is a fake feeling of separation of concerns with the Asp.Net’s code behind
Automated test could be challenging.
That’s cool… But

Web standards
HTTP
CSS
Javascript
REST (Representational State Transfer), represents an application in terms of resources, instead of SOAP, the Asp.Net web service base technology
Agile and TDD
The Web development today is

So… Welcome, Asp.Net MVC
WEB

Asp.Net MVC “tenets”
Be extensible, maintainable and flexible
Be testable
Have a tight control over HTML and HTTP
Use convention over configuration
DRY: don’t repeat yourself
Separation of concerns

The MVC pattern

Separation of concerns
Separation of concerns comes naturally with MVC
Controller knows how to handle a request, that a View exist, and how to use the Model (no more)
Model doesn’t know anything about a View
View doesn’t know there is a Controller

Asp.Net > Asp.Net MVC
Based on the .Net platform (quite straightforward  )
Master page
Forms authentication
Membership and Role providers
Profiles
Internationalization
Cache
Asp.Net MVC is built on (the best part of) Asp.Net

Asp.Net and Asp.Net MVC run-time stack

Demo
First Asp.NetMVC application

Asp.Net MVC
The structure of the project

Asp.Net MVC projects have some top-level (and core) directories that you don’t need to setup in the config:
Controllers, where you put the classes that handle the request
Models, where you put the classes that deal with data
Views, where you put the UI template files
Scripts, where you put Javascript library files and scripts (.js)
Content, where you put CSS and image files, and so on
App_Data, where you put data files
Convention over configuration

Models, Controllers and Views

The Models
Classes that represent your application data
Contain all the business, validation, and data acccess logic required by your application
Three different kind of Model:
data being posted on the Controller
data being worked on in the View
domain-specific entities from you business tier
You can create your own Data Model leveraging the most recommend data access technologies
The representation of our data

An actual Data Model using Entity Framework 4.0

ViewModel Pattern
Additional layer to abstract the data for the Views from our business tier
Can leverage the strongly typed View template features
The Controller has to know how to translate from the business tier Entity to the ViewModel one
Enable type safety, compile-time checking and Intellisense
Useful specially in same complex scenarios
Create a class tailored on our specific View scenarios

publicActionResultCustomer(int id)
{
ViewData[“Customer”] = MyRepository.GetCustomerById(id);
ViewData[“Orders”] = MyRepository.GetOrderforCustomer(id);
return View();
}
publicclassCustomerOrderMV
{
Customer CustomerData {get; set;}
Order CustomerOrders{ get; set;}
}
publicActionResult Customer(int id)
{
CustomerOrderMVcustOrd = MyRepository.GetCustomerOrdersById(id);
ViewData.Model = custOrd;
return View();
}
Model vs.ViewModel

Validation
Validation and business rule logic are the keys for any application that work with data
Schema validation comes quite free if you use OR/Ms
Validation and Business Rule logic can be quite easy too using the Asp.Net MVC 2 Data Annotations validation attributes (actually these attributes were introduced as a part of the Asp.Net Dynamic Data)
Adding Validation Logic to the Models

[MetadataType(typeof(Blog_Validation))]
publicpartialclassBlog
{
}
[Bind(Exclude = "IdBlog")]
publicclassBlog_Validation
{
[Required(ErrorMessage= "Title required")]
[StringLength(50, ErrorMessage = "…")]
[DisplayName("Blog Title")]
publicString Title { get; set; }
[Required(ErrorMessage = "Blogger required")]
[StringLength(50, ErrorMessage = “…")]
publicString Blogger { get; set; }ù
…
}
Data Annotations validation
How to add validation to the Model through Metadata

Demo
Asp.Net MVC Models

The controllers are responsible for responding to the user request
Have to implement at least the IController interface, but better if you use the ControllerBaseor the Controller abstract classes (with more API and resources, like the ControllerContext and the ViewData, to build your own Controller)
The Controllers

using System;
usingSystem.Web.Routing;
namespaceSystem.Web.Mvc
{
// Summary:Defines the methods that are required for a controller.
publicinterfaceIController
{
// Summary: Executes the specified request context.
// Parameters:
// requestContext:The request context.
void Execute(RequestContextrequestContext);
}
}
usingSystem.Web;
usingSystem.Web.Mvc;
publicclassSteoController : IController
{
publicvoid Execute(System.Web.Routing.RequestContextrequestContext)
{
HttpResponseBase response = requestContext.HttpContext.Response;
response.Write("<h1>Hello MVC World!</h1>");
}
}
My own Controller

publicinterfaceIHttpHandler
{
voidProcessRequest(HttpContext context);
boolIsReusable { get; }
}
publicinterfaceIController
{
voidExecute(RequestContextrequestContext);
}
They look quite similar, aren’t they?
The two methods respond to a request and write back the output to a response
The Page class, the default base class for ASPX pages in Asp.Net, implements the IHttpHandler.
This reminds me something…

The Action Methods
All the public methods of a Controller class become Action methods, which are callable through an HTTP request
Actually, only the public methods according to the defined Routes can be called

The ActionResult
Actions, as Controller’s methods, have to respond to user input, but they don’t have to manage how to display the output
The pattern for the Actions is to do their own work and then return an object that derives from the abstract base class ActionResult
ActionResultadhere to the “Command pattern”, in which commands are methods that you want the framework to perform in your behalf

The ActionResult
publicabstract class ActionResult
{
public abstract voidExecuteResult(ControllerContext context);
}
publicActionResultList()
{
ViewData.Model= // get data from a repository
returnView();
}

ActionResult types
EmptyResult
ContentResult
JsonResult
RedirectResult
RedirectToRouteResult
ViewResult
PartialViewResult
FileResult
FilePathResult
FileContentResult
FileStreamResult
JavaScriptResult
Asp.Net MVC has several types to help handle the response

Demo
Asp.Net MVC Controllers

The Views are responsible for providing the User Interface (UI) to the user
The View receive a reference to a Model and it transforms the data in a format ready to be presented
The Views

Asp.Net MVC’s View
Handles the ViewDataDictionary and translate it into HTML code
It’s an Asp.Net Page, deriving from ViewPage (System.Web.Mvc.ViewPage) which itself derives from Page (System.Web.UI.Page)
By default it doesn’t include the “runat=server”, that you can add by yourself manually, if you want to use some server controls in your View (better to use only the “view-only” controls)
Can take advantage of the Master Page, building Views on top of the Asp.Net Page infrastructure

Asp.Net MVC Views’ syntax
You will use <%: %> syntax (often referred to as “code nuggets”) to execute code within the View template.
There are two main ways you will see this used:
Code enclosed within <% %> will be executed
Code enclosed within <%: %> will be executed, and the result will be output to the page

Demo
Views, Strongly Typed View, specify a View

Html Helpers
Html.Encode
Html.TextBox
Html.ActionLink, RouteLink
Html.BeginForm
Html.Hidden
Html.DropDownList
Html.ListBox
Html.Password
Html.RadioButton
Html.Partial, RenderPartial
Html.Action, RenderAction
Html.TextArea
Html.ValidationMessage
Html.ValidationSummary
Methods shipped with Asp.Net MVC that help to deal with the HTML code.
MVC2 introduced also the strongly typed Helpers, that allow to use Model properties using a Lambda expression instead of a simple string

Partial View
Asp.Net MVC allow to define partial view templates that can be used to encapsulate view rendering logic once, and then reuse it across an application (help to DRY-up your code)
The partial View has a .ascx extension and you can use like a HTML control

The default Asp.Net MVC project just provide you a simple Partial View: the LogOnUserControl.ascx
<%@ControlLanguage="C#"Inherits="System.Web.Mvc.ViewUserControl" %>
<%
if (Request.IsAuthenticated) {
%>
Welcome <b><%:Page.User.Identity.Name %></b>!
[ <%:Html.ActionLink("Log Off", "LogOff", "Account") %> ]
<%
}
else {
%>
[ <%:Html.ActionLink("Log On", "LogOn", "Account") %> ]
<%
}
%>
Partial View Example
A simple example out of the box

Ajax
You can use the most popular libraries:
Microsoft Asp.Net Ajax
jQuery
Can help to partial render a complex page (fit well with Partial View)
Each Ajax routine will use a dedicated Action on a Controller
With Asp.Net Ajax you can use the Ajax Helpers that come with Asp.Net MVC:
Ajax.BeginForm
AjaxOptions
IsAjaxRequest
…
It’s not really Asp.Net MVC but can really help you to boost your MVC application

Routing
Routing in Asp.Net MVC are used to:
Match incoming requests and maps them to a Controller action
Construct an outgoing URLs that correspond to Contrller action
How Asp.Net MVC manages the URL

Routing vs URL Rewriting
They are both useful approaches in creating separation between the URL and the code that handles the URL, in a SEO (Search Engine Optimization) way
URL rewriting is a page centric view of URLs (eg: /products/redshoes.aspx rewritten as /products/display.aspx?productid=010)
Routing is a resource-centric (not only a page) view of URLs. You can look at Routing as a bidirectional URL rewriting

publicstaticvoidRegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new{ controller = "Home", action = "Index", id = UrlParameter.Optional} // Parameter defaults );
}
protectedvoidApplication_Start()
{
AreaRegistration.RegisterAllAreas();
RegisterRoutes(RouteTable.Routes);
}
}
Defining Routes
The default one…

Route URL patterns

StopRoutingHandler and IgnoreRoute
You can use it when you don’t want to route some particular URLs.
Useful when you want to integrate an Asp.Net MVC application with some Asp.Net pages.

Filters
Filters are declarative attribute based means of providing cross-cutting behavior
Out of the box action filters provided by Asp.Net MVC:
Authorize: to secure the Controller or a Controller Action
HandleError: the action will handle the exceptions
OutputCache: provide output caching to for the action methods

Demo
A simple Filter (Session Expire)

Asp.Net MVC was made with TDD in mind, but you can use also without it (if you want… )
A framework designed with TDD in mind from the first step
You can use your favorite Test Framework
With MVC you can test the also your UI behavior (!)

Demo

Let’s start the Open Session:Asp.Net vs. Asp.Net MVC

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Asp.Net MVC Intro

by Stefano Paluello, Software Dev and Architect at www.pastesoft.com on Jan 14, 2011

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Asp.Net MVC Intro Presentation Transcript