authorize.net error code 128 Extending the controller in .NET framework

Printing ANSI/AIM Code 128 in .NET framework Extending the controller

box, you re not out of luck the MVC Framework gives you full control to implement your own controller, which could act radically differently than the one provided in the framework.

The default controller implementation comes with some specific ideas about how action methods are selected, executed, and extended. This functionality comes from the Controller base class in the ASP.NET MVC framework, which is the default implementation of the IController interface. IController is a simple interface that provides a single method, Execute(), and you could choose to implement it directly. By implementing this interface, you can still use the routing and controller factory functionality of the framework and push the rest of the framework to the side. You can see the IController interface definition in figure 9.1. A second extensibility option is available that isn t as lean as implementing IController. The framework contains a ControllerBase Figure 9.1 The IController interface exposes a single method, Execute(). class that provides the most basic properties for managing ViewData and TempData. The ControllerBase class is listed in figure 9.2. It s a pretty minimal class but it still lets you take advantage of some concepts that are shared with the view. Although the interface and base class extensibility points exist in the framework, few developers and projects trade the productivity built into the framework s controller class for the power and extra work that s needed to implement their own IController implementation. The same goes for using the ControllerBase class. We needn t sacrifice productivity because a number of Figure 9.2 The ControllerBase class provides integration with routing as well as HttpContext. extensibility points are built into the Controller class. We ll cover them next.

Actions are the methods that control the main logic of each server request, but not all methods of a controller class qualify to be an action. The requirements for a method to be web-callable as an action method are well documented on Microsoft s ASP.NET MVC site (www.asp.net/mvc). To be considered as an action, the method must meet the following requirements:

It must be public. It can t be static. It can t be an extension method. It can t be a constructor, getter, or setter. It can t have open generic types. It can t be a method of the Controller base class. It can t be a method of the ControllerBase base class. It can t contain ref or out parameters.

If a method doesn t meet all these requirements, it isn t an action method. Now that you can identify action methods, we ll discuss how to modify their behavior.

The first extensibility point of actions is through an ActionFilter. This extensibility point allows you to intercept the execution of an action and inject behavior before or after the action is executed. This is similar to aspect-oriented programming, which is a technique for applying cross-cutting concerns to a code base without having lots of duplicate code to maintain. The easiest way to implement an action filter is to create a class that inherits from ActionFilterAttribute, although it s also possible to override methods on the Controller class itself. Figure 9.3 shows the methods of ActionFilterAttribute that can be overridden to modify an action. This attribute implements the IActionFilter and IResultFilter interfaces, each of which provides different extensibility points.

The new ChildActionOnlyAttribute action filter shipped with MVC 2. This filter implements the IAuthorizationFilter interface and is used by the framework to ensure that an action is only called from the RenderAction() method within a view. An action that has this attribute can t be called through a top-level route and isn t web callable. The code in listing 9.1 shows the ChildActionOnlyAttribute applied to the ChildAction method.