DXA - Setting of location and file name of custom 404 error page

Question

See: Redirect to 404.html doesnt work on second time

We found that in case of a 404 error, DXA wants to open a custom page "error-404.html" in the Home Structure Group, like in the example website. However, we want to change the location of that page to a sub Structure Group folder (any maybe the name as well) but we cannot find where that setting is set. Can anyone tell us where that is set?

14-4-2021 Additional info after suggested solution of Atila Sos. This is the code that I created for the override of the NotFound method but somehow it is not hit when a non existing page is requested in the browser. What do I do wrong?

using System.Web; 
using System.Web.Mvc; 
using Sdl.Web.Common; 
using Sdl.Web.Common.Logging; 
using Sdl.Web.Common.Models; 
using Sdl.Web.Mvc.Configuration; 
using Sdl.Web.Mvc.Formats; 
namespace Sdl.Web.Mvc.Controllers 
{
public class CustomPageController : PageController 
{ 
/// <summary> 
/// Render a custom file not found page 
/// </summary> 
/// <returns>404 page or HttpException if there is none</returns> 
[FormatData] 
public override ActionResult NotFound() 
{ 
using (new Tracer()) 
{     
string notFoundPageUrl = WebRequestContext.Localization.Path + "/Subfolder/Errors" + "/404"; 
PageModel pageModel; 
try 
{ 
pageModel = ContentProvider.GetPageModel(notFoundPageUrl, WebRequestContext.Localization); 
} 
catch (DxaItemNotFoundException ex) 
{ 
Log.Error(ex); 
throw new HttpException(404, ex.Message); 
} 
SetupViewData(pageModel); 
PageModel model = EnrichModel(pageModel) as PageModel ?? pageModel; 
WebRequestContext.PageModel = model; 
Response.StatusCode = 404; 
return View(model.MvcData.ViewName, model); 
} 
} 
} 
} 

Answer 1

The location is hardcoded within DXA's source code. Take a look at the PageController's NotFound method.

string notFoundPageUrl = WebRequestContext.Localization.Path + "/error-404";

The method is virtual so you can override it. Truth be told, it would be better to have direct control over just the location :)