Due to the reliance on Server.Transfer it seems that the internal implementation of ResponseRewrite isn't compatible with MVC.
This seems like a glaring functionality hole to me, so I decided to re-implement this feature using a HTTP module, so that it just works. The solution below allows you to handle errors by redirecting to any valid MVC route (including physical files) just as you would do normally.
<customErrors mode="RemoteOnly" redirectMode="ResponseRewrite">
<error statusCode="404" redirect="404.aspx" />
<error statusCode="500" redirect="~/MVCErrorPage" />
</customErrors>
This has been tested on the following platforms;
- MVC4 in Integrated Pipeline Mode (IIS Express 8)
- MVC4 in Classic Mode (VS Development Server, Cassini)
- MVC4 in Classic Mode (IIS6)
namespace Foo.Bar.Modules {
/// <summary>
/// Enables support for CustomErrors ResponseRewrite mode in MVC.
/// </summary>
public class ErrorHandler : IHttpModule {
private HttpContext HttpContext { get { return HttpContext.Current; } }
private CustomErrorsSection CustomErrors { get; set; }
public void Init(HttpApplication application) {
System.Configuration.Configuration configuration = WebConfigurationManager.OpenWebConfiguration("~");
CustomErrors = (CustomErrorsSection)configuration.GetSection("system.web/customErrors");
application.EndRequest += Application_EndRequest;
}
protected void Application_EndRequest(object sender, EventArgs e) {
// only handle rewrite mode, ignore redirect configuration (if it ain't broke don't re-implement it)
if (CustomErrors.RedirectMode == CustomErrorsRedirectMode.ResponseRewrite && HttpContext.IsCustomErrorEnabled) {
int statusCode = HttpContext.Response.StatusCode;
// if this request has thrown an exception then find the real status code
Exception exception = HttpContext.Error;
if (exception != null) {
// set default error status code for application exceptions
statusCode = (int)HttpStatusCode.InternalServerError;
}
HttpException httpException = exception as HttpException;
if (httpException != null) {
statusCode = httpException.GetHttpCode();
}
if ((HttpStatusCode)statusCode != HttpStatusCode.OK) {
Dictionary<int, string> errorPaths = new Dictionary<int, string>();
foreach (CustomError error in CustomErrors.Errors) {
errorPaths.Add(error.StatusCode, error.Redirect);
}
// find a custom error path for this status code
if (errorPaths.Keys.Contains(statusCode)) {
string url = errorPaths[statusCode];
// avoid circular redirects
if (!HttpContext.Request.Url.AbsolutePath.Equals(VirtualPathUtility.ToAbsolute(url))) {
HttpContext.Response.Clear();
HttpContext.Response.TrySkipIisCustomErrors = true;
HttpContext.Server.ClearError();
// do the redirect here
if (HttpRuntime.UsingIntegratedPipeline) {
HttpContext.Server.TransferRequest(url, true);
}
else {
HttpContext.RewritePath(url, false);
IHttpHandler httpHandler = new MvcHttpHandler();
httpHandler.ProcessRequest(HttpContext);
}
// return the original status code to the client
// (this won't work in integrated pipleline mode)
HttpContext.Response.StatusCode = statusCode;
}
}
}
}
}
public void Dispose() {
}
}
}
Usage
Include this as the final HTTP module in your web.config
<system.web>
<httpModules>
<add name="ErrorHandler" type="Foo.Bar.Modules.ErrorHandler" />
</httpModules>
</system.web>
<!-- IIS7+ -->
<system.webServer>
<modules>
<add name="ErrorHandler" type="Foo.Bar.Modules.ErrorHandler" />
</modules>
</system.webServer>
