ASP.Net MVC Filters

ASP.Net MVC Filters

In ASP.NET MVC, controllers define action methods that usually have a one-to-one relationship with possible user interactions, such as clicking a link or submitting a form. For example, when the user clicks a link, a request is routed to the designated controller, and the corresponding action method is called.

Sometimes you want to perform logic either before an action method is called or after an action method runs. To support this, ASP.NET MVC provides filters. Filters are custom classes that provide both a declarative and programmatic means to add pre-action and post-action behavior to controller action methods.

Asp.Net MVC filters are used to implement additional logic at the time of code execution.

Types of filters and sequence of Execution.

1.      Authentication

2.      Authorization

3.      Action

4.      Result

5.      Exception

Authentication Filters

Authentication filter runs before any other filter or action method. Authentication confirms that you are a valid or invalid user. Action filters implements the IAuthenticationFilter interface. 

Authorization Filters

The AuthorizeAttribute and RequireHttpsAttribute are the examples of Authorization Filters. Authorization Filters are responsible for checking User Access; these implement the IAuthorizationFilterinterface in the framework. These filters used to implement authentication and authorization for controller actions. For example, the Authorize filter is an example of an Authorization filter.

Action Filters

Action Filter is an attribute that you can apply to a controller action or an entire controller. This filter will be called before and after the action starts executing and after the action has executed.

Action filters implement the IActionFilter interface that have two methods OnActionExecuting andOnActionExecuted. OnActionExecuting runs before the Action and gives an opportunity to cancel the Action call. These filters contain logic that is executed before and after a controller action executes, you can use an action filter, for instance, to modify the view data that a controller action returns.

Result Filters

The OutputCacheAttribute class is an example of Result Filters. These implement the IResultFilter interface which like the IActionFilter has OnResultExecuting and OnResultExecuted. These filters contains logic that is executed before and after a view result is executed. Like if you want to modify a view result right before the view is rendered to the browser.

Exception Filters

The HandleErrorAttribute class is an example of ExceptionFilters. These implement the IExceptionFilter interface and they execute if there are any unhandled exceptions thrown during the execution pipeline. These filters can be used as an exception filter to handle errors raised by either your controller actions or controller action results.