o_19mgorv9t13a3ko71fev19l81mqa.pdf

IExceptionFilter {
public void OnException(ExceptionContext filterContext) {
if (!filterContext.ExceptionHandled &&
filterContext.Exception is ArgumentOutOfRangeException) {
filterContext.Result
= new
RedirectResult("∼/Content/RangeErrorPage.html");
filterContext.ExceptionHandled = true;
}
}
}
}
This exception filter handles ArgumentOutOfRangeException instances by redirecting the user’s browser to a
file called RangeErrorPage.html in the Content folder. Notice that I have derived the
RangeExceptionAttribute class from the FilterAttribute class, in addition to implementing the
IExceptionFilter interface. In order for a .NET attribute class to be treated as an MVC filter, the class has to
implement the IMvcFilter interface. You can do this directly, but the easiest way to create a filter is to derive your class
from FilterAttribute, which implements the required interface and provides some useful basic features, such as
handling the default order in which filters are processed (which I will come to later in this chapter).
Applying the Exception Filter
I need to do some groundwork before I can test the exception filter. First, I need to create a Content folder in the example
project and create the RangeErrorPage.html file within it. This is the file that I will direct users to when the exception
is handled and you can see the contents of the file in Listing 18-22.
Listing 18-22. The Contents of the RangeErrorPage.html File
Range Error
Sorry
One of the arguments was out of the expected range.
Next, I need to add an action method to the Home controller which will throw the exception I want to demonstrate. You can
see the addition in Listing 18-23.
Listing 18-23. Adding a New Action in the HomeController.cs File
using System;
using System.Web.Mvc;
using Filters.Infrastructure;
namespace Filters.Controllers {
public class HomeController : Controller {
[Authorize(Users = "admin")]
public string Index() {
476