Way back in 2009, the MVC Futures assembly introduced “strongly-typed action helpers”.  They allowed you to render links using lambda expressions pointing directly to the actions on your controller, rather than using strings:

<%= Html.ActionLink<HomeController>( c => c.Index() ) %>

Other benefits included:

  • Intellisense and refactoring in Visual Studio
  • Compile-time validation
  • Check if user is authorized for an action (automatically hide or disable links)

Unfortunately there was a performance overhead associated with all this (http://haacked.com/archive/2009/06/02/alternative-to-expressions.aspx) that led to some interesting alternatives, including the T4MVC project.

However, there’s still hope for strongly-typed helpers.  You can find an alternative implementation here that aims to resolve most of the performance concerns.

The main classes of interest are:

  • ActionTemplate – Captures controller and action name from action expression.  Defers getting “baked in” parameter values until (and if) needed.
  • ActionBuilder – Created from ActionTemplate, captures optional parameter values.  Renders links and forms (calls HtmlHelper.ActionLink or BeginForm).

Previously, most of the performance hit was from compiling the argument expressions. This version tries a few alternative approaches first, like extracting the argument value directly if it’s a ConstantExpression, and allowing named parameters in the ActionBuilder instance (if it finds a value in the parameters collection, it doesn’t bother looking at the argument part of the action expression).

Some of the features demonstrated (in HomeController.cs) include:

  • Using ActionBuilders as properties of the view model.  The controller defines the target actions, and the view just renders them as links.
  • Using a static ActionTemplate instance to minimize the work needed to generate a list of parameterized ActionBuilders.  Note the template expression simply passes ‘null’ as the argument; in this case it’ll never get used as the ActionBuilders are given their own parameter values.
  • A dummy authentication mechanism to demonstrate automatically disabled links (log in with password “password” to enable the actions marked with the Authorize attribute).

You can get all the source code here Smile

About these ads