Wrox Press What's New in ASP.NET MVC 2 (2010).pdf

Simone Chiaretta

What’s New

in ASP.NET

MVC 2?

Wiley Publishing, Inc.

Updates, source code, and Wrox technical support at www.wrox.com

Contents

Introducing ASP.NET MVC 2

Runs on Visual Studio 2008 and Visual Studio 2010

Templated Helpers and Model Metadata

HiddenInputAttribute

How to Write Custom Templates

Validation

Client-Side Validation

Custom Validation Rules

Areas

Asynchronous Controllers

Why Asynchronous Operations Matter

The Anatomy of an Asynchronous Controller

How to Implement an Async Controller

When to Use an Async Controller

RenderAction and Child Actions

Strongly Typed UI Helpers

Enhancements to ModelBinders

Default Value

Increasing Security with HTTPS

Avoiding the JSON Array Attack

Short Notation for AcceptVerbs Attribute

Overriding the HTTP Verb

Binary Binding

Automatic HTML-Encoding

Enhanced Visual Studio Tooling

Summary

About Simone Chiaretta

What’s New in

ASP.NET MVC 2?

Introducing ASP.NET MVC 2

ASP.NET MVC is the new Framework for building web applications released by Microsoft at the

beginning of 2009. It adopts an approach that is completely different from the traditional Web

Forms one that was introduced with the release of the .NET Framework in 2002: Instead of using

an event-based programming style, ASP.NET MVC implements the Model-View-Controller

pattern so that it’s easier to achieve a better separation of concerns and it’s easier to make the

application extensible and testable.

Version 1.0 has been downloaded and used by almost 1 million developers in the first year after its

final release, becoming more and more popular every month. But some thought that it was still too

unfinished for enterprise development, mainly because it was missing some important features

like client-side validation. In March 2010, after one year, version 2 of the Framework has been

released, whose main focus is to enhance productivity and make the Framework ready for

enterprise development.

ASP.NET MVC 2 is built on top of the first release and is completely compatible with it, which

means that all of your knowledge, skills, and even the code you wrote continue to work when you

move forward to the new version.

ASP.NET MVC 2 adds the following new features, which will be covered in detail through the rest

of this Wrox Blox:

❏

Templated Helpers — Make it easier and faster to create the HTML to display and edit data.

❏

Client-Side Validation — Brings the same powerful metadata-based validation to the client.

❏

Areas — Allow you to organize a big application into smaller logical sections.

What’s New in ASP.NET MVC 2?

❏

Asynchronous Controllers — Solve the same issue addressed by the asynchronous pages in

traditional Web Forms by performing long-running tasks on a separate thread to free up

resources on the server.

❏

Child Actions — Make easy encapsulation of logic and presentation possible.

❏

Strongly Typed UI Helpers — Add a new strongly typed flavor to the existing UI Helpers.

And in addition to these main features, other smaller features and enhancements to the existing ones

have been introduced, together with a better Visual Studio (VS) integration, especially in VS2010.

To make the migration to the new version easier, ASP.NET MVC 2 can be installed side-by-side with

ASP.NET MVC 1.0, which means that on the same server you can have applications written in V1 and

others written in V2, making it easier to adopt the new version for new applications while taking your

time to upgrade the older ones.

This Wrox Blox will not discuss what the ASP.NET MVC Framework is and how it works, but it is meant

to guide a developer who is already familiar with the first version of the Framework through the new

features that have been introduced into the second version. If you want to learn the basics of the

Framework or if you find yourself struggling with some concepts while you are reading this Wrox Blox,

I suggest that you read one of the books that treat the first version — such as Beginning ASP.NET

MVC 1.0 by myself and Keyvan Nayyeri (Wrox, 2009; ISBN: 978-0-470-43399-7) or Professional

ASP.NET MVC 1.0 by Rob Conery, Scott Hanselman, Phil Haack, and Scott Guthrie (Wrox, 2009;

ISBN: 978-0-470-38461-9) — and then come back to read about the new features.

Runs on Visual Studio 2008 and Visual Studio 2010

ASP.NET MVC 2 can be used in Visual Studio 2008 (VS 2008), running on .NET 3.5 Service Pack 1, and in

the newly released Visual Studio 2010 (VS 2010), running on .NET 4.

If you want to use MVC 2 with Visual Studio 2010, there is nothing you have to do: The Framework

comes in-the-box with the new Integrated Development Environment (IDE). But if you want to use

MVC 2 with Visual Studio 2008, you have to download it from www.asp.net/mvc/ or via the Web

Platform Installer.

Other than this different way of getting the Framework, there are a few subtle differences between

running on .NET 3.5 SP1 and on .NET4 because some features are available only with .NET 4. All the

samples and code snippets will be developed with VS 2010 and .NET 4, but when the syntax is different

or when a feature is available on .NET 4, it will be made very clear in the text.

Templated Helpers and Model Metadata

With the goal to enhance productivity, Templated Helpers are probably the most important new feature

of MVC 2.

Templated Helpers automatically build the UI needed to represent or edit data based on the data model

itself and on a set of metadata that, in the default implementation, is retrieved from the attributes

applied to the Model.

What’s New in ASP.NET MVC 2?

For example, a property of the data model can be marked with an attribute that specifies that

the property represents HTML text. The Templated Helper can automatically render the text using

a user interface (UI) specifically designed for HTML code instead of just treating it as a normal

string, or it could present the user with a WYSIWYG textbox to edit the string instead of a

normal textbox.

All the magic is done via the following HTML Helpers:

❏

Html.EditorFor — Builds the UI to edit each property in the object specified as the parameter.

❏

Html.DisplayFor — Builds the UI to display the value of each property in the object specified

as the parameter.

These two methods accept a lambda expression as the parameter, but if you prefer, there are also another

two flavors:

❏

Html.Editor and Html.Display — Do the exact same thing as the EditorFor and

DisplayFor , but these are used if you prefer to pass the name of the object as a string instead

of as an expression.

❏

Html.EditorForModel and Html.DisplayForModel — Works directly on the full Model

of the View.

Listing 1 shows how to write the form to edit the Model of a View.

Listing 1: The Edit View using the Templated Helpers

<% using (Html.BeginForm()) {%>

<legend>Fields</legend>

<%: Html.EditorForModel() %>

<p>

</p>

</fieldset>

<% } %>

Listing 2 contains the definition of the View Model, with the attributes applied to its properties.

Listing 2: The Post View Model

using System.Web.Mvc;

using System.ComponentModel.DataAnnotations;

using System.ComponentModel;

public class Post

continued

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