Is ASP.NET MVC 1 forwards compatible with ASP.NET MVC 2?

asp.net, asp.net-mvc, backwards-compatibility

Solution

There have been breaking changes.

If you want a 1.0 project to run on 2.0, it does look for things in different places; so you'd have to migrate the application to 2.0..

Here are the changes that could possibly 'break' (current as of Preview 2):

Changes in Preview 2

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 of the HTML helpers is now `MvcHtmlString` instead of a `string`. Note that if you use ASP.NET MVC 2 and the new helpers with 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; they delegate to the `ModelMetadata` property to retrieve the value.

Changes in Preview 1

`DefaultControllerFactory` class changes break custom controller factories that derive from it

This change affects custom controller factories that derive from `DefaultControllerFactory` . The DefaultControllerFactory class was fixed by removing the `RequestContext` property and instead passing the request context instance to the protected virtual methods `GetControllerInstance` and `GetControllerType`.

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.

Known Issues

The Add View dialog box throws a NullReferenceException when the Create strongly-typed view check box is checked, a View Content selection other than “Empty” is selected, and a View data class type name is specified for a type that does exist. When specifying a type name, either use the drop-down list to select the type name or type the fully-qualified type name. For types that do not exist, you must set View Content to “Empty”.

Problem

Original source