How do you render Headless ASP.NET to present a Sitecore page as 404?

Question

As per Sitecore's example code for ASP.NET Headless you can have your default controller method look like this:

[UseSitecoreRendering]
public IActionResult Index(Route route) {
    var request = HttpContext.GetSitecoreRenderingContext();

    if (request.Response.HasErrors) {
        foreach (var error in request.Response.Errors) {
            switch (error) {
                case ItemNotFoundSitecoreLayoutServiceClientException notFound:
                    Response.StatusCode = (int)HttpStatusCode.NotFound;
                    return View("NotFound", request.Response.Content.Sitecore.Context);
                case InvalidRequestSitecoreLayoutServiceClientException badRequest:
                case CouldNotContactSitecoreLayoutServiceClientException transportError:
                case InvalidResponseSitecoreLayoutServiceClientException serverError:
                default:
                    throw error;
            }
        }
    }

    return View(route);
}

But I want to display a Sitecore page as the 404 page instead of a regular View inside the ASP.NET rendering host.

Let's say I have a page at the following path in Sitecore: /sitecore/content/MySite/Home/ErrorPages/404

How would I go about rendering that specific page when the rendering host encounters a "NotFound" scenario? This has to work with model binding, of course.

I guess I have to do something instead of Return View("NotFound", request.Response.Content.Sitecore.Context); but what?

Answer 1

You can use:

return Redirect("/ErrorPages/404");

or

return Redirect("http://myErrorPage");

instead of:

return View("NotFound", request.Response.Content.Sitecore.Context);

Updated:

I don't see OOTB ways if a 404 status code is needed, but as an option, it is possible to use one of the standard approaches like the one below:

1. Create your own RedirectResultWithStatusCode (it can be inherited from RedirectResult) with the option to pass statusCode

2. Override the existing RedirectResultExecutor, that is registered:

   services.TryAddSingleton<IActionResultExecutor<RedirectResult>, RedirectResultExecutor>();

And then override ExecuteAsync, so it might look something like that:

public override Task ExecuteAsync(ActionContext context, RedirectResult result)
{
    var redirectResultWithStatusCode = result as RedirectResultWithStatusCode;
    if (redirectResultWithStatusCode == null)
    {
        return base.ExecuteAsync(context, result);
    }

    // My logic is here

    /*
    context.HttpContext.Response.StatusCode = redirectResultWithStatusCode.StatusCode;
    context.HttpContext.Response.Headers[HeaderNames.Location] = result.Url;
    */

    return Task.CompletedTask;
}
                        

Answer 2

We have implemented it as a custom Pipeline with Sitecore JSS therefore it will work also with ASP.NET Headless. Of course in integrated mode. In headless mode you need to approach this with different logic on FE / renderer side.

This solution is not redirecting visitors to 404 page. It keeps current URL which is much better.

Idea is to catch when Context.Item equals null with few other conditions so you are sure that Sitecore would show regular 404 error page. Your pipeline will be patched before Sitecore's NotFound pipeline. You will then set Context Item to $site$/Error Pages/404 and set proper HTTP Error code to Not Found.

Code for Processor:

using System.Linq;
using System.Net;
using System.Web;
using System.Web.Routing;
using Sitecore;
using Sitecore.Pipelines.HttpRequest;
using Sitecore.XA.Foundation.SitecoreExtensions.Extensions;

namespace Client.Foundation.Pipelines
{
    public class ItemNotFound : HttpRequestProcessor
    {
        public override void Process(HttpRequestArgs args)
        {
            using (new PerformanceProfiler(nameof(ItemNotFound)))
            {
                if (Context.Item == null
                && Context.Site != null
                && Context.Database != null

                && string.IsNullOrEmpty(Context.Page.FilePath)
                && RouteTable.Routes.GetRouteData(args.HttpContext) == null
                && !args.PermissionDenied)
                {
                    string[] localPathElements = args.LocalPath.Split('/');

                    string contextItemStartPath = Context.Site.StartPath;

                    Context.Item = Context.Database.GetItem(contextItemStartPath + "/ErrorPages/404");

                    HttpContext.Current.Response.TrySkipIisCustomErrors = true;
                    HttpContext.Current.Response.StatusCode = (int)HttpStatusCode.NotFound;
                }
            }
        }
    }
}

Config entry to introduce processor:

<?xml version="1.0" encoding="utf-8" ?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
    <sitecore>
        <pipelines>
            <httpRequestBegin>
                <processor type="Client.Foundation.Pipelines.ItemNotFound, Client.Foundation"
                           patch:before="processor[@type='Sitecore.XA.Feature.ErrorHandling.Pipelines.HttpRequestBegin.ItemNotFoundResolver, Sitecore.XA.Feature.ErrorHandling']" />
            </httpRequestBegin>
        </pipelines>
    </sitecore>
</configuration>