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How can I properly handle 404 in ASP.NET MVC?
I've made the changes outlined at 404 Http error handler in Asp.Net MVC (RC 5) and I'm still getting the standard 404 error page. Do I need to change something in IIS?
I've investigated A LOT on how to properly manage 404s in MVC (specifically MVC3), and this, IMHO is the best solution I've come up with:
In global.asax:
public class MvcApplication : HttpApplication
{
protected void Application_EndRequest()
{
if (Context.Response.StatusCode == 404)
{
Response.Clear();
var rd = new RouteData();
rd.DataTokens["area"] = "AreaName"; // In case controller is in another area
rd.Values["controller"] = "Errors";
rd.Values["action"] = "NotFound";
IController c = new ErrorsController();
c.Execute(new RequestContext(new HttpContextWrapper(Context), rd));
}
}
}
ErrorsController:
public sealed class ErrorsController : Controller
{
public ActionResult NotFound()
{
ActionResult result;
object model = Request.Url.PathAndQuery;
if (!Request.IsAjaxRequest())
result = View(model);
else
result = PartialView("_NotFound", model);
return result;
}
}
Edit:
If you're using IoC (e.g. AutoFac), you should create your controller using:
var rc = new RequestContext(new HttpContextWrapper(Context), rd);
var c = ControllerBuilder.Current.GetControllerFactory().CreateController(rc, "Errors");
c.Execute(rc);
Instead of
IController c = new ErrorsController();
c.Execute(new RequestContext(new HttpContextWrapper(Context), rd));
(Optional)
Explanation:
There are 6 scenarios that I can think of where an ASP.NET MVC3 apps can generate 404s.
Generated by ASP.NET:
Generated by ASP.NET MVC:
Scenario 2: URL matches a route, but specifies a controller that doesn't exist.
Scenario 3: URL matches a route, but specifies an action that doesn't exist.
Manually generated:
Scenario 4: An action returns an HttpNotFoundResult by using the method HttpNotFound().
Scenario 5: An action throws an HttpException with the status code 404.
Scenario 6: An actions manually modifies the Response.StatusCode property to 404.
Objectives
(A) Show a custom 404 error page to the user.
(B) Maintain the 404 status code on the client response (specially important for SEO).
(C) Send the response directly, without involving a 302 redirection.
Solution Attempt: Custom Errors
<system.web>
<customErrors mode="On">
<error statusCode="404" redirect="~/Errors/NotFound"/>
</customErrors>
</system.web>
Problems with this solution:
Solution Attempt: HTTP Errors
<system.webServer>
<httpErrors errorMode="Custom">
<remove statusCode="404"/>
<error statusCode="404" path="App/Errors/NotFound" responseMode="ExecuteURL"/>
</httpErrors>
</system.webServer>
Problems with this solution:
Solution Attempt: HTTP Errors with Replace
<system.webServer>
<httpErrors errorMode="Custom" existingResponse="Replace">
<remove statusCode="404"/>
<error statusCode="404" path="App/Errors/NotFound" responseMode="ExecuteURL"/>
</httpErrors>
</system.webServer>
Problems with this solution:
Solution Attempt customErrors and HTTP Errors
<system.web>
<customErrors mode="On">
<error statusCode="404" redirect="~/Errors/NotFound"/>
</customError>
</system.web>
and
<system.webServer>
<httpErrors errorMode="Custom">
<remove statusCode="404"/>
<error statusCode="404" path="App/Errors/NotFound" responseMode="ExecuteURL"/>
</httpErrors>
</system.webServer>
Problems with this solution:
People that have troubled with this before even tried to create their own libraries (see http://aboutcode.net/2011/02/26/handling-not-found-with-asp-net-mvc3.html). But the previous solution seems to cover all the scenarios without the complexity of using an external library.