How to ignore routes in ASP.NET Core?

Question

Previously, one would add something like this to Global.aspx.cs, which is gone in .NET Core:

  routes.IgnoreRoute("{*favicon}", new { favicon = @"(.*/)?favicon.ico(/.*)?" });

Here's what I currently have in my Startup.cs (for .NET Core):

  app.UseDefaultFiles();

  app.UseStaticFiles();

  app.UseMvc(routes =>
  {
      routes.MapRoute(
          name: "default",
          template: "{controller=Home}/{action=Index}/{id?}");

      routes.MapSpaFallbackRoute(
          name: "spa-fallback",
          defaults: new { controller = "Home", action = "Index" });
  });

The problem is that in MVC (pre-Core) routes was a RouteCollection and in .NET Core it's a Microsoft.AspNetCore.Routing.IRouteBuilder so IgnoreRoute is not a valid method.

Lansquenet

Answer 1

If you want to make a static file accessible without the routing condition, simply use the build-in StaticFiles Middleware. Activate it with app.UseStaticFiles(); in Configure Method and put your static files in wwwroot directory. They're availible on HOST/yourStaticFile

For more information, refer here

Overpay

Answer 2

You could write middleware for this.

public void Configure(IApplciationBuilder app) {
    app.UseDefaultFiles();

    // Make sure your middleware is before whatever handles 
    // the resource currently, be it MVC, static resources, etc.
    app.UseMiddleware<IgnoreRouteMiddleware>();

    app.UseStaticFiles();
    app.UseMvc();
}

public class IgnoreRouteMiddleware {

    private readonly RequestDelegate next;

    // You can inject a dependency here that gives you access
    // to your ignored route configuration.
    public IgnoreRouteMiddleware(RequestDelegate next) {
        this.next = next;
    }

    public async Task Invoke(HttpContext context) {
        if (context.Request.Path.HasValue &&
            context.Request.Path.Value.Contains("favicon.ico")) {

            context.Response.StatusCode = 404;

            Console.WriteLine("Ignored!");

            return;
        }

        await next.Invoke(context);
    }
}

Swampland

Thanks very much for this, but to boil it down: I must replace one line of code with an entire custom route? Seems kinda bloated. – Lansquenet

Perhaps? There may be a way in .NET Core that more directly addresses your concern. Perhaps via the Routing middleware. I simply have not run into it. I would read this document then check out the source code to get something more definitive: docs.asp.net/en/latest/fundamentals/routing.html – Swampland

This solution makes sense but should be more specific, looking for a path containing the string provided means potentially paths you don't want to match will be matched, and this isn't very optimal either, it would be better in terms of performance to simply not use middleware and keep the number of routes to a minimum. – Opportunism

In order to address Bonner's concerns Contains(...) should be replaced with StartsWith("/favicon.ico").Otherwise, an excellent answer. – Olds

This works, but see my answer below for a simpler solution. – Pompon

Answer 3

.NET Core 3.1

For .NET Core 3.1 with endpoint routing, this seems like the easiest way. You don't need to build a middleware just for this simple case.

app.UseEndpoints(endpoints =>
{
    endpoints.MapGet("/favicon.ico", async (context) =>
    {
        context.Response.StatusCode = 404;
    });
    // more routing
});

The original question is about ignoring routes. If you do want to serve a favicon, you can add HTML markup in _Layout.cshtml like this. This technique allows more control over where the icon is served from.

<link rel="icon" href="@Url.Content("~/images/favicon.ico")" />

I am using both of these techniques in my code.

Pompon

Ah, nice to see this has gotten better! – Swampland

Except that the goal isn't to return a 404 error but the actual favicon.ico file. – Lansquenet

Please see my new edits @JeffGuillaume – Pompon

Answer 4

inside public void Configure

add

app.Map("/favicon.ico", delegate { });

Apollonius

If you're using swagger and also want to ignore the controller (still requires this answer), also add [ApiExplorerSettings(IgnoreApi = true)] will remove from the swagger doc – Guerdon

This answer works, but it throws an exception System.InvalidOperationException: The request reached the end of the pipeline without executing the endpoint: '/favicon.ico HTTP: GET'. Please register the EndpointMiddleware using 'IApplicationBuilder.UseEndpoints(...)' if using routing. in .NET Core 3.1. – Pompon

@Pompon Good to know. Original answer was for .NET Core 1.0.1 – Apollonius

Answer 5

Allow favicon requests to be parsed by the route handler, and keep your routes to a minimum. Avoid using middleware, this just adds additional complexity to your code and means all other requests must go through the middleware before the route handler, which is worse in terms of performance for busy websites. For websites that aren't busy you would just be wasting your time worrying about this.

See https://github.com/aspnet/Routing/issues/207

Opportunism

Answer 6

In ASP.NET Core, you can write a constrained catch-all route template. To do so, in your ASP.NET Core example, replace the call to routes.MapSpaFallbackRoute with the following:

// Returns the home/index page for unknown files, except for
// favicon.ico, in which case a 404 error is returned.
routes.MapRoute(
    name: "spa-fallback",
    template: "{*url:regex(^(?!favicon.ico).*$)}",
    defaults: new { Controller = "Home", action = "Index" });

Gunk