ASP.NET MVC 4 - Exception Handling Not Working

Question

When an error occurs in my ASP.NET MVC 4 application, I would like to customize a view for the user depending on the type of error. For example, page not found or an except

Answer 1

I also went on a seamingly endless journey of reading SO answers and assorted blog postings trying to get custom error pages to work. Below is what finally worked for me.

The first step is to use IIS Express for debugging instead of the built-in Cassini web server to "guarantee" that the debug experience will mirror the live environment.

Create a controller to handle application errors and add an action for each custom error you will handle. The action should do any logging, set the status code, and return the view.

public class ErrorsController : Controller
{
    // 404
    [HttpGet]
    public ActionResult NotFound()
    {
        Response.StatusCode = (int)HttpStatusCode.NotFound;
        return View();
    }

    // I also have test actions so that I can verify it's working in production.
    [HttpGet]
    public ActionResult Throw404()
    {
        throw new HttpException((int)HttpStatusCode.NotFound, "demo");
    }
}

Configure the customErrors section in web.config to redirect to your custom error actions.

Add the httpErrors section to system.webServer and set the errorMode to Detailed in web.config. Why this works is a mystery to me, but this was the key.

Add a catchall route last to the defined routes to direct 404s to the custom page.

            // catchall for 404s
        routes.MapRoute(
            "Error",
            "{*url}",
            new {controller = "Errors", action = "NotFound"});

You may also want to create a custom HandleErrorAttribute and register it as a global filter to log 500 errors.

These steps worked for me in both development (IIS Express) and production (IIS7) environments. You need to change customErrors mode="On" to see the effect in development.