ASP.NET MVC 3 “Preview 1” includes several nice controller-specific enhancements.

Global Filters

ASP.NET MVC supports the ability to declaratively apply “cross-cutting” logic using a mechanism called “filters”.  You can specify filters on Controllers and Action Methods today using an attribute syntax like so:

Developers often want to apply some filter logic across all controllers within an application.  ASP.NET MVC 3 now enables you to specify that a filter should apply globally to all Controllers within an application.  You can now do this by adding it to the GlobalFilters collection.  A RegisterGlobalFilters() method is now included in the default Global.asax class template to provide a convenient place to do this (it is then called by the Application_Start() method):

The filter resolution logic in MVC 3 is flexible so that you can configure a global filter that only applies conditionally if certain conditions are met (for example: debugging is enabled, or if a request uses a particular http verb, etc).  Filters can also now be resolved from a Dependency Injection (DI) container – more on that below.

New Dynamic ViewModel Property

ASP.NET MVC Controllers have supported a “ViewData” property that enables you to pass data to a view template using a late-bound dictionary API.  For example:

The “ViewData” API is still supported in ASP.NET MVC 3.  MVC 3 augments it, though, with a new “ViewModel” property on Controller that is of type “dynamic” – and which enables you to use the new dynamic language support within VB and C# to pass ViewData items using a slightly cleaner syntax than the current dictionary API.  Now you can alternatively write the following code to achieve the same result as above:

You do not need to define any strongly-typed classes to use the ViewModel property.  Because it is a “dynamic” property you can instead just get/set properties on it and it will resolve them dynamically at runtime.  It internally stores the property name/value pairs within the ViewData dictionary.