Only Map existing Blazor Pages(Razor Components) in the pipeline? - asp.net-core

Question

The usual pattern for Blazor (server) apps, is that at the end pf program.cs there is app.MapFallbackToPage("/_Host");
That will result in ALL request paths, that match no earlier endpoint, executing the Blazor App. Sure the Blazor App has a <NotFound> Renderfragment, but that will still result in establishing the SignalR and so on. What if I want to display a static file (.html) from wwwroot or a specfic RAZOR PAGE (.cshtml), which doesnt establlish a websocket for all those cases where the route does NOT EXIST IN ANY BLAZOR PAGE ???
NavigationManager.NavigateTo cannot be used directly inside the BuildRenderTree markup of the <NotFound> ... I could maybe put a component inside there that redirects OnInitialized ... but that would still first require the SignalR.
How can I completely avoid Blazor/SignalR for URLs that don't exist in the Blazor App ?
Idea: I could try to add ALL POSSIBLE Blazor-routes as fallbacks and the most general fallback to some static file or Razor Page... but that seems LIKE A LOT OF DOUBLE WORK and very error prone... is there no way?
app.MapFallbackToPage("~/Admin/{*clientroutes:nonfile}", "/_Host");
app.MapFallbackToPage("~/SomeRoute/More/{*clientroutes:nonfile}", "/_Host");
app.MapFallbackToPage("~/SomePage/{*clientroutes:nonfile}", "/_Host");
app.MapFallbackToPage("/NotValidRoute");
Edit:
#Reason:
I wanted to have a single fallback page (razor page or static) for all routes/urls that don't match any target in the app. But sadly as it seems, that conflicts with blazor'S client side routing. since the server-side routing does not know, which routes should be handled by blazor, it also cannot know, which routes would not map to anything (razor pages and blazor combined). Other please correct me here.

Answer 1

There's server-side routing and client-side routing. On the server side, the middleware pipeline runs first, handling static files and server defined routes, including the fallback route. Fallback routes are routes that don't match static file requests and have the lowest priority, so they are not preferred over other matching routes.
Server-side routing has no idea what routes are going to match on the client-side. That data model is separate. What's happening is, when no server route matches, the host page is rendered, which bootstraps the client. Now you've transitioned to client-side routing and cannot re-enter (without a change to refresh the browser)
What if I want to display a static file (.html) from wwwroot or a specfic RAZOR PAGE (.cshtml), which doesnt establlish a websocket for all those cases where the route does NOT EXIST IN ANY BLAZOR PAGE ???
That requires knowing what routes exists on the client.
Idea: I could try to add ALL POSSIBLE Blazor-routes as fallbacks and the most general fallback to some static file or Razor Page... but that seems LIKE A LOT OF DOUBLE WORK and very error prone... is there no way?
Possible using the <NotFound> component to run some JavaScript and redirect the browser to a fixed route on the server.
Edit:
Another would be to build that found all routable razor components and map them all as fallback routes to "_Host".
Something like this (untested):
// This should match wherever components are declared.
var types = typeof(Program).Assembly.GetTypes();
foreach (var type in types)
{
if (typeof(ComponentBase).IsAssignableFrom(type) && type.GetCustomAttribute<RouteAttribute>() is { } routeAttribute)
{
var route = routeAttribute.Template;
endpointRouteBuilder.MapFallbackToPage(route, "/_Host");
}
}

Answer 2

It partly depends on how your app is hosted. In IIS, you can add applications to any website, which are basically websites of any type you want with a "/path" added.
Currently, my company's main app is "ABCsite.com," and my Blazor app is "ABCsite.com/Blazor"