asp.net-mvc Action filters Action filter usage locations (global, controller, action)
Example
You can place action filters at three possible levels:
- Global
- Controller
- Action
Placing a filter globally means it will execute on requests to any route. Placing one on a controller makes it execute on requests to any action in that controller. Placing one on an action means it runs with the action.
If we have this simple action filter:
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = true)]
public class CustomActionFilterAttribute : FilterAttribute, IActionFilter
{
private readonly string _location;
public CustomActionFilterAttribute(string location)
{
_location = location;
}
public void OnActionExecuting(ActionExecutingContext filterContext)
{
Trace.TraceInformation("OnActionExecuting: " + _location);
}
public void OnActionExecuted(ActionExecutedContext filterContext)
{
Trace.TraceInformation("OnActionExecuted: " + _location);
}
}
We can add it on global level by adding it to the global filter collection. With the typical ASP.NET MVC project setup, this is done in App_Start/FilterConfig.cs.
public class FilterConfig
{
public static void RegisterGlobalFilters(GlobalFilterCollection filters)
{
filters.Add(new CustomActionFilterAttribute("Global"));
}
}
We can also add it on controller and action level like so in a controller:
[CustomActionFilter("HomeController")]
public class HomeController : Controller
{
[CustomActionFilter("Index")]
public ActionResult Index()
{
return View();
}
}
If we run the application and look at the Output window, we will see the following messages:
iisexpress.exe Information: 0 : OnActionExecuting: Global
iisexpress.exe Information: 0 : OnActionExecuting: HomeController
iisexpress.exe Information: 0 : OnActionExecuting: Index
iisexpress.exe Information: 0 : OnActionExecuted: Index
iisexpress.exe Information: 0 : OnActionExecuted: HomeController
iisexpress.exe Information: 0 : OnActionExecuted: Global
As you can see, when the request comes in, the filters are executed:
- Global
- Controller
- Action
Excellent examples of filters placed on global level include:
- Authentication filters
- Authorization filters
- Logging filters
