How to replace Blazor default "soft 404" with an actual 404 status code response - http-status-code-404

Question

The default Blazor approach to 404 is to create a soft 404 in App.razor, but I would like to adhere to search engine best practices to actually return the 404 status code while displaying a 404 page on Azure.
I tried to remove the element in App.razor to see if I could force a 404, however, that did not compile.
Any suggestions?

Answer 1

I use this code. It works well.
I created Error404Layout. I use this layout for NotFound part.
<Router AppAssembly="#typeof(Program).Assembly" PreferExactMatches="#true">
<Found Context="routeData">
<RouteView RouteData="#routeData" DefaultLayout="#typeof(MainLayout)" />
</Found>
<NotFound>
<LayoutView Layout="#typeof(Error404Layout)">
<h2>Oops! That page can't be found.</h2>
</LayoutView>
</NotFound>
Error404Layout content below
#inherits LayoutComponentBase
#using Microsoft.AspNetCore.Http
#inject IHttpContextAccessor httpContextAccessor
#Body
#code {
protected override void OnInitialized()
{
httpContextAccessor.HttpContext.Response.StatusCode = 404;
}
}
You have to add this code in startup.cs / services method
public void ConfigureServices(IServiceCollection services)
{
....
services.AddHttpContextAccessor();
}
I can see 404 status code

Answer 2

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/http-context?view=aspnetcore-3.1 does state:
Additionally, again for security reasons, you must not use
IHttpContextAccessor within Blazor apps. Blazor apps run outside of
the context of the ASP.NET Core pipeline and the HttpContext isn't
guaranteed to be available within the IHttpContextAccessor, nor it is
guaranteed to be holding the context that started the Blazor app.
So you need to create a wrapper around IHttpContextAccessor to limit this when Blazor is being server side prerendered.
I was able to return 404 http status codes when using server side prerendering in the Blazor WebAssembly App (ASP.Net Core Hosted) Template
When I pointed the browser to http://localhost/fetchdata it returned a page. I wanted this to return a 404 status code as an example. This was possible using dependency injection and a stub class.
In BlazorApp1.Client I added a IResponse.cs file:
namespace BlazorApp1.Client {
public interface IResponse {
void SetNotFound();
}
}
In BlazorApp1.Client I added a ResponseStub.cs file:
namespace BlazorApp1.Client {
public class ResponseStub : IResponse {
public void SetNotFound() {
// Do nothing if we are browser side
}
}
}
In FetchData.razor in BlazorApp1.Client I added:
#inject BlazorApp1.Client.IResponse Response
and in the code section:
protected override void OnInitialized() {
Response.SetNotFound();
}
In Program.cs in BlazorApp1.Client I added:
builder.Services.AddScoped<IResponse, ResponseStub>();
Then in BlazorApp1.Server, in Startup.cs I added under ConfigureServices:
services.AddHttpContextAccessor();
services.AddScoped<IResponse, Response>();
and under Configure I replaced:
endpoints.MapFallbackToFile("index.html");
with:
endpoints.MapFallbackToPage("/_Host");
Then create the Server implementation of IResponse in Response.cs:
using BlazorApp1.Client;
using Microsoft.AspNetCore.Http;
using System.Net;
namespace BlazorApp1.Server {
public class Response : IResponse {
private readonly IHttpContextAccessor _httpContextAccessor;
public Response(IHttpContextAccessor accessor) {
_httpContextAccessor = accessor;
}
public void SetNotFound() {
_httpContextAccessor.HttpContext.Response.StatusCode = (int)HttpStatusCode.NotFound;
}
}
}
And finally I create a _Host.cshtml file in BlazorApp1.Server/Pages:
#page "/fallback"
#namespace BlazorPrerendering.Server.Pages
#using BlazorApp1.Client
#addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
#{
Layout = "_Layout";
}
<app>
<component type="typeof(App)" render-mode="ServerPrerendered" />
</app>
<div id="blazor-error-ui">
An unhandled error has occurred.
Reload
<a class="dismiss">🗙</a>
</div>
<script src="_framework/blazor.webassembly.js"></script>

Answer 3

#ergin-Çelik Your solution works very well. I only had to add the following check because I got an error that the response had already been sent.
I have add this as answer because code formatting is better here.
protected override void OnInitialized()
{
if (_httpContextAccessor.HttpContext != null &&
!_httpContextAccessor.HttpContext.Response.HasStarted)
{
_httpContextAccessor.HttpContext.Response.StatusCode = (int) HttpStatusCode.NotFound;
}
}