How do I resolve "Request reached the end of the middleware pipeline without being handled by application code."?

Question

I am attempting to convert our public API into using just the single Program.cs format as part of our .NET8 update but despite the application building and running, when I try to hit a route I get a 404 and in the debug output I get "Request reached the end of the middleware pipeline without being handled by application code." I have stripped out all but the default "app.Xyz" that come with the dotnet template but the issue still remains. My "app" section of the Program.cs now looks like this:

var app = builder.Build();

var listener = app.Services.GetRequiredService<DiagnosticListener>();
var observer = ActivatorUtilities.CreateInstance<AnalysisDiagnosticAdapter>(app.Services);
using var disposable = listener.SubscribeWithAdapter(observer);


app.UseHttpsRedirection();
app.UseRouting();
app.UseUserAuthentication();
app.UseAuthorization();

app.MapControllerRoute(
    name: "Default",
    pattern:"{controller=Home}/{action=Index}/{id?}"
    );

app.Run();

I added in the DiagnosticAdapter to see if that would help but it doesn't really tell me anything that the default debug output did.

I can add a test route in this file, using app.MapGet(); which works and returns correctly but any controller external to this return the 404 error.

Answer 1

You should register the controllers. Try to replacing app building line with below:

builder.Services.AddControllers();
var app = builder.Build();