What is New in MVC 2 (Brad Wilson)

8/8/2019 What is New in MVC 2 (Brad Wilson)

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What’s New in ASP.NET MVC 2 1

Copyright © 2010 Microsoft Corporation

What’s New in ASP.NET MVC 2

This document describes new features and improvements introduced in ASP.NET MVC 2.

Introduction ......................................................................................................................................1

Upgrading an ASP.NET MVC 1.0 Project to ASP.NET MVC 2 .................................................................2

New Features.....................................................................................................................................2

Templated Helpers .................................................................................................................................... 2

Areas ......................................................................................................................................................... 2

Support for Asynchronous Controllers ..................................................................................................... 4

Support for DefaultValueAttribute in Action-Method Parameters .......................................................... 4

Support for Binding Binary Data with Model Binders ............................................................................... 5ModelMetadata and ModelMetadataProvider Classes ............................................................................ 6

Support for DataAnnotations Attributes .................................................................................................. 6

Model-Validator Providers ........................................................................................................................ 7

Client-Side Validation ................................................................................................................................ 7

New Code Snippets for Visual Studio 2010 ............................................................................................... 7

New RequireHttpsAttribute Action Filter ................................................................................................. 7

Overriding the HTTP Method Verb ........................................................................................................... 7

New HiddenInputAttribute Class for Templated Helpers ......................................................................... 9

Html.ValidationSummary Helper Method Can Display Model-Level Errors ........................................... 10T4 Templates in Visual Studio Generate Code that is Specific to the Target Version of the .NETFramework .............................................................................................................................................. 10

API Improvements ........................................................................................................................... 10

Breaking Changes ............................................................................................................................. 11

Disclaimer ........................................................................................................................................ 13

Introduction

ASP.NET MVC 2 builds on ASP.NET MVC 1.0 and introduces a large set of enhancements and features

that are focused on increasing productivity. This release is compatible with ASP.NET MVC 1.0, so all your

knowledge, skills, code, and extensions for ASP.NET MVC 1.0 continue to apply.

For more information about ASP.NET MVC, visit the following resources:





ASP.NET MVC documentation on MSDN

The ASP.NET MVC Web site

The ASP.NET MVC forums

Upgrading an ASP.NET MVC 1.0 Project to ASP.NET MVC 2

ASP.NET MVC 2 can be installed side by side with ASP.NET MVC 1.0 on the same server, which gives

application developers flexibility in choosing when to upgrade an ASP.NET MVC 1.0 application to

ASP.NET MVC 2. For information on how to upgrade, see the document Upgrading an ASP.NET MVC 1.0

Application to ASP.NET MVC 2.

New Features

This section describes features that have been introduced in the MVC 2 release.

Templated Helpers

Templated helpers let you automatically associate HTML elements for edit and display with data types.

For example, when data of type System.DateTime is displayed in a view, a date-picker UI element can be

automatically rendered. This is similar to how field templates work in ASP.NET Dynamic Data. For more

information, see Using Templated Helpers to Display Data on the MSDN Web site.

Areas

Areas let you organize a large project into multiple smaller sections in order to manage the complexity

of a large Web application. Each section (“area”) typically represents a separate section of a large Web

site and is used to group related sets of controllers and views. For more information, see Walkthrough:

Organizing an ASP.NET MVC Application by Areas on the MSDN Web site.

To create a new area, in Solution Explorer, right-click the project, click Add, and then click Area. This

displays a dialog box that prompts you for the area name. After you enter the area name, Visual Studio

adds a new area to the project.

The following figure shows an example layout for a project with two areas, Admin and Blogs.

http://go.microsoft.com/fwlink/?LinkId=159758


http://asp.net/mvc/

http://asp.net/mvc/

http://forums.asp.net/1146.aspx


http://go.microsoft.com/fwlink/?LinkID=185459

















http://asp.net/mvc/






When you create an area, Visual Studio adds a class that derives from AreaRegistration to each area.

This class is required in order to register the area and its routes, as shown in the following example:

namespace MyApplication.Areas.Blog {

public class BlogAreaRegistration : AreaRegistration {

public override string AreaName {

get { return "blog"; }

}

public override void RegisterArea(AreaRegistrationContext context) {

context.MapRoute(

"blog_default",

"blog/{controller}/{action}/{id}",

new { action = "Index", id = UrlParameter.Optional }

);

context.MapRoute(

"blog_whatsnew",





"whats-new",

new { action = "WhatsNew", id = UrlParameter.Optional }

);

}

}

}

The default project template for ASP.NET MVC 2 includes a call to the RegisterAllAreas method in the

code for the Global.asax file. This method registers each area in the project by looking for all types

that derive from the AreaRegistration class, instantiating an instance of the type, and then calling the

RegisterArea method on the instance. The following example shows how this is done.

public class MyMvcApplication : HttpApplication {

void App_Start() {

AreaRegistration.RegisterAllAreas();

RegisterRoutes(RouteTable.Routes);

}

public static void RegisterRoutes(RouteCollection routes) {

routes.MapRoute("default", "{controller}/{action}/{id}", ...);

}

}

If you do not specify the namespace in the RegisterArea method by calling the context.Namespaces.Add

method, the namespace of the registration class is used by default.

Support for Asynchronous Controllers

ASP.NET MVC 2 now allows controllers to process requests asynchronously. This can lead to

performance gains by allowing servers which frequently call blocking operations (like network requests)

to call non-blocking counterparts instead. For more information, see the Using an Asynchronous

Controller in ASP.NET MVC topic on MSDN.

Support for DefaultValueAttribute in Action-Method Parameters

The System.ComponentModel.DefaultValueAttributeclass allows a default value to be supplied for theargument parameter to an action method. For example, assume that the following default route is

defined:

{controller}/{action}/{id}

Also assume that the following controller and action method is defined:

http://msdn.microsoft.com/en-us/library/ee728598(v=VS.100).aspx










public class ArticleController {

public ActionResult View(int id, [DefaultValue(1)]int page) {

}

}

Any of the following request URLs will invoke the View action method that is defined in the precedingexample.

/Article/View/123

/Article/View/123?page=1 (Effectively the same as the previous request)

/Article/View/123?page=2

Without the DefaultValueAttribute attribute, the first URL from the preceding list would not work,

because the page argument is a non-nullable value type whose value has not been provided.

If your code is written in Visual Basic 2010 or Visual C# 2010, you can use optional parameters instead of

the DefaultValueAttribute attribute, as shown in the following example:

Function View(ByVal id As Integer, Optional ByVal page As Integer = 1) _

As ActionResult

' ...

End Function

public ActionResult MyAction(int id, int page = 1) {

// ...

}

Support for Binding Binary Data with Model Binders

There are two new overloads of the Html.Hidden helper that encode binary values as base-64-encoded

strings:

public static string Hidden(this HtmlHelper htmlHelper, string name, Binary

value);

public static string Hidden(this HtmlHelper htmlHelper, string name, byte[]

value);

A typical use is to embed a timestamp for an object in the view. For example, your application might

include the following Product object:

public class Product {

//... other properties ...

public byte[] TimeStamp {





get;

set;

}

}

An edit form can render the TimeStamp property in the form as shown in the following example:

<%@ Page Inherits="ViewPage<Product>" %>

<%= Html.Hidden("TimeStamp", Model.TimeStamp) %>

This markup renders a hidden input element with the timestamp value as a base-64-encoded string that

resembles the following example:

<input type="hidden" name="TimeStamp" value="QVNQLk5FVCBNVkMgaXMgZnVuIQ==" />

This form might be posted to an action method that has an argument of type Product, as shown in the

following example:

public ActionResult Edit(Product p) {

// p.TimeStamp is populated from the form

}

In the action method, the TimeStamp property is populated correctly because the posted base-64-

encoded string is converted to a byte array.

ModelMetadata and ModelMetadataProvider Classes

The ModelMetadataProvider class provides an abstraction for obtaining metadata for the model within

a view. MVC 2 includes a default provider that makes available the metadata that is exposed by the

attributes in the System.ComponentModel.DataAnnotations namespace. It is possible to create

metadata providers that provide metadata from other data stores, such as databases or XML files.

The ViewDataDictionary class exposes a ModelMetadata object that contains the metadata that is

extracted from the model by the ModelMetadataProvider class. This enables the templated helpers to

consume this metadata and adjust their output accordingly.

For more information, see the documentation for the ModelMetadata and ModelMetadataProvider

classes.

Support for DataAnnotations Attributes

ASP.NET MVC 2 supports using the RangeAttribute, RequiredAttribute, StringLengthAttribute, and

RegexAttribute validation attributes (defined in the System.ComponentModel.DataAnnotations

namespace) when you bind to a model in order to provide input validation.

http://msdn.microsoft.com/en-us/library/system.web.mvc.modelmetadataprovider(VS.100).aspx












For more information, see How to: Validate Model Data Using DataAnnotations Attributes on the MSDN

Web site. A sample project that illustrates the use of these attributes is available for download at

http://go.microsoft.com/fwlink/?LinkId=157753.

Model-Validator Providers

The model-validation provider class represents an abstraction that provides validation logic for the

model. ASP.NET MVC includes a default provider based on validation attributes that are included in the

System.ComponentModel.DataAnnotations namespace. You can also create your own validation

providers that define custom validation rules and custom mappings of validation rules to the model. For

more information, see the documentation for the ModelValidatorProvider class.

Client-Side Validation

The model-validator provider class exposes validation metadata to the browser in the form of JSON-

serialized data that can be consumed by a client-side validation library. ASP.NET MVC 2 includes a client

validation library and adapter that supports the DataAnnotations namespace validation attributes noted

earlier. The provider class also enables you to use other client-validation libraries by writing an adapter

that processes the JSON data and calls into the alternate library.

New Code Snippets for Visual Studio 2010

A set of HTML code snippets for ASP.NET MVC 2 is installed with Visual Studio 2010. To view a list of

these snippets, in the Tools menu, select Code Snippets Manager. For the language, select HTML, and

for location, select ASP.NET MVC 2. For more information about how to use code snippets, see the

Visual Studio documentation.

New RequireHttpsAttribute Action Filter

ASP.NET MVC 2 includes a new RequireHttpsAttribute class that can be applied to action methods and

controllers. By default, the filter redirects a non-SSL (HTTP) request to the SSL-enabled (HTTPS)

equivalent.

Overriding the HTTP Method Verb

When you build a Web site by using the REST architectural style, HTTP verbs are used to determine

which action to perform for a resource. REST requires that applications support the full range of

common HTTP verbs, including GET, PUT, POST, and DELETE.

ASP.NET MVC 2 includes new attributes that you can apply to action methods and that feature compact

syntax. These attributes enable ASP.NET MVC to select an action method based on the HTTP verb. In the






http://msdn.microsoft.com/en-us/library/system.web.mvc.ModelValidatorProvider(VS.100).aspx










New HiddenInputAttribute Class for Templated Helpers

You can apply the new HiddenInputAttribute attribute to a model property to indicate whether a hidden

input element should be rendered when displaying the model in an editor template. (The attribute sets

an implicit UIHint value of HiddenInput). The attribute’s DisplayValue property lets you specify

whether the value is displayed in editor and display modes. When DisplayValue is set to false, nothing isdisplayed, not even the HTML markup that normally surrounds a field. The default value for

DisplayValue is true.

You might use HiddenInputAttribute attribute in the following scenarios:

When a view lets users edit the ID of an object and it is necessary to display the value as well as to

provide a hidden input element that contains the old ID so that it can be passed back to the

controller.

When a view lets users edit a binary property that should never be displayed, such as a timestamp

property. In that case, the value and surrounding HTML markup (such as the label and value) are not

displayed.

The following example shows how to use the HiddenInputAttribute class.

public class ProductViewModel {

[HiddenInput] // equivalent to [HiddenInput(DisplayValue=true)]

public int Id { get; set; }

public string Name { get; set; }

[HiddenInput(DisplayValue=false)]public byte[] TimeStamp { get; set; }

}

When the attribute is set to true (or no parameter is specified), the following occurs:

In display templates, a label is rendered and the value is displayed to the user.

In editor templates, a label is rendered and the value is rendered in a hidden input element.

When the attribute is set to false, the following occurs:

In display templates, nothing is rendered for that field.

In editor templates, no label is rendered and the value is rendered in a hidden input element.





Html.ValidationSummary Helper Method Can Display Model-Level Errors

Instead of always displaying all validation errors, the Html.ValidationSummary helper method has a new

option to display only model-level errors. This enables model-level errors to be displayed in the

validation summary and field-specific errors to be displayed next to each field.

T4 Templates in Visual Studio Generate Code that is Specific to the Target

Version of the .NET Framework

A new property is available to T4 files from the ASP.NET MVC T4 host that specifies the version of the

.NET Framework that is used by the application. This enables T4 templates to generate code and markup

that is specific to a version of the .NET Framework. In Visual Studio 2008, the value is always .NET 3.5.

In Visual Studio 2010, the value is either .NET 3.5 or .NET 4.

API Improvements

This section describes changes to existing ASP.NET MVC types and members.

Added a protected virtual CreateActionInvoker method in the Controller class. This method is

invoked by the ActionInvoker property of Controller and allows for lazy instantiation of the invoker if

no invoker is already set.

Added a protected virtual HandleUnauthorizedRequest method in the AuthorizeAttribute class. This

enables filters that derive from AuthorizeAttribute to control the behavior when authorization fails.

Added an Add(string key, object value) method in the ValueProviderDictionary class. This enables

you to use the dictionary initializer syntax for ValueProviderDictionary , as in the following example:

Controller c = new MyController();

c.ValueProvider = new ValueProviderDictionary(null) {

{ "example1", "example1Value" },

{ "example2", "example2Value" },

{ "example3", new int[] { 1, 2, 3 } }

};

Added a get_object method in the Sys.Mvc.AjaxContext class. This is a JavaScript method that is

similar to the get_data method, but if the content type of the response is application/json,

get_object returns the JSON object. Added an ActionDescriptor property in the AuthorizationContext class.

Added a UrlParameter.Optional token that can be used to work around problems when binding to a

model that contains an ID property when the property is absent in a form post. For more detail, see

the entry ASP.NET MVC 2 Optional URL Parameters on Phil Haack’s blog.

http://haacked.com/archive/2010/02/12/asp-net-mvc-2-optional-url-parameters.aspx








Breaking Changes

The following changes might cause errors in existing ASP.NET MVC 1.0 applications.

Change in property validation behavior for classes that implement IDataErrorInfo

For model objects that use IDataErrorInfo to perform validation, every property is validated, regardless

of whether a new value was set. In ASP.NET MVC 1.0, only properties that had new values set were

validated. In ASP.NET MVC 2, the Error property of IDataErrorInfo is called only if all the property

validators were successful.

IIS script mapping script is no longer available in the installer

The IIS script-mapping script is a command-line script that is used to configure script maps for IIS 6 and

for IIS 7 in Classic mode. The script-mapping script is not needed if you use the Visual Studio

Development Server or if you use IIS 7 in Integrated mode. The scripts are available as a separateunsupported download on the ASP.NET CodePlex site.

The Html.Substitute helper method in MVC Futures is no longer available

Due to changes in the rendering behavior of MVC view engines, the Html.Substitute helper method does

not work and has been removed.

The IValueProvider interface replaces all uses of IDictionary<string, ValueProviderResult>

Every property or method argument that accepted IDictionary<string, ValueProviderResult> in MVC 1.0

now accepts IValueProvider . This change affects only applications that include custom value providers or

custom model binders. Examples of properties and methods that are affected by this change include the

following:

The ValueProvider property of the ControllerBase and ModelBindingContext classes.

The TryUpdateModel methods of the Controller class.

New CSS classes were added in the Site.css file

The Site.css file in the ASP.NET MVC project templates has been updated to include new styles used by

the validation functionality and by the templated helpers.

Helpers now return an MvcHtmlString object

In order to take advantage of the new HTML-encoding expression syntax in ASP.NET 4, the return type

for HTML helpers is now MvcHtmlString instead of a string. If you use ASP.NET MVC 2 and the new

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helpers on ASP.NET 3.5, you will not be able to take advantage of the HTML-encoding syntax; the new

syntax is available only when you run ASP.NET MVC 2 on ASP.NET 4.

JsonResult now responds only to HTTP POST requests

In order to mitigate JSON hijacking attacks that have the potential for information disclosure, by default,the JsonResult class now responds only to HTTP POST requests. Ajax GET calls to action methods that

return a JsonResult object should be changed to use POST instead. If necessary, you can override this

behavior by setting the new JsonRequestBehavior property of JsonResult . For more information about

the potential exploit, see the blog post JSON Hijacking on Phil Haack’s blog.

Model and ModelType property setters on ModelBindingContext are obsolete

A new settable ModelMetadata property has been added to the ModelBindingContext class. The new

property encapsulates both the Model and the ModelType properties. Although the Model and

ModelType properties are obsolete, for backward compatibility the property getters still work; theydelegate to the ModelMetadata property to retrieve the value.

Changes to the DefaultControllerFactory class break custom controller factories that derive

from it

The DefaultControllerFactory class was fixed by removing the RequestContext property. In place of this

property, the request context instance is passed to the protected virtual GetControllerInstance and

GetControllerType methods. This change affects custom controller factories that derive from

DefaultControllerFactory .

Custom controller factories are often used to provide dependency injection for ASP.NET MVC

applications. To update the custom controller factories to support ASP.NET MVC 2, change the method

signature or signatures to match the new signatures, and use the request context parameter instead of

the property.

“Area” is a now a reserved route-value key

The string “area” in Route values now has special meaning in ASP.NET MVC, in the same way that

“controller” and “action” do. One implication is that if HTML helpers are supplied with a route-value

dictionary containing “area”, the helpers will no longer append “area” in the query string.

If you are using the Areas feature, make sure to not use {area} as part of your route URL.

http://haacked.com/archive/2009/06/25/json-hijacking.aspx








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What is New in MVC 2 (Brad Wilson)

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