Razor Pages should only listenen to specific route

Question

I have a project with an existing FastEndpoints REST API. Nothing special, pretty much the default configuration:

app.UseFastEndpoints(x => {
    x.Endpoints.Configurator = definition => {
        definition.Description(desc => desc.ProducesProblemFE<CommonErrorResponse>(500));
        definition.Description(desc => desc.ProducesProblemFE<ErrorResponse>());
    };
    x.Endpoints.Filter = ep => true;
});

Now I want to add the Duende IdentityServer, which I guess doesn't matter too much, because the real problem are the Razor pages of this package. Again, nothing special:

builder.Services.AddRazorPages();

The problem now is, that the Razor pages take precedence over the REST API. That means, if I want to go to GET users/self I get shown a razor page instead of the correct data or an HTTP error.

So what I'd like to do is one of the following:

• configure Razor to only listen to a specific route
• configure FastEndpoints to override Razor's setting for its route

I could not find anything on either of this frameworks (only a solution for MVC), so I'm asking here: how do I do that?

Answer 1

the following middleware order seems to work:

var bld = WebApplication.CreateBuilder(args);
bld.Services
   .AddFastEndpoints()
   .AddRazorPages();

var app = bld.Build();

if (!app.Environment.IsDevelopment())
    app.UseExceptionHandler("/Error");

app.UseRouting()
   .UseAuthorization()
   .UseFastEndpoints();
app.MapStaticAssets();
app.MapRazorPages()
   .WithStaticAssets();
app.Run();

test endpoint:

sealed class TestEndpoint : EndpointWithoutRequest
{
    public override void Configure()
    {
        Get("test");
        AllowAnonymous();
    }

    public override async Task HandleAsync(CancellationToken c)
    {
        await SendAsync("hello...");
    }
}

making a get request to /test shows the following api response:

GET http://localhost:5234/test

HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Date: Wed, 08 Jan 2025 17:34:24 GMT
Server: Kestrel
Transfer-Encoding: chunked

"hello..."

Response code: 200 (OK); Time: 3ms (3 ms); Content length: 10 bytes (10 B)