How deeply does ASP.NET Core in Action, 3e cover routing middleware?

Explains two-stage request handling and middleware placement, but defers detailed Razor Page handler selection.

Routing middleware

As explained in ASP.NET Core in Action, 3e

UseRouting is an ASP.NET Core extension method that adds routing middleware to a web application's request pipeline.

Routing middleware selects an endpoint for an incoming request by matching its URL to a registered route. The request then continues through the middleware pipeline. Endpoint middleware executes the selected endpoint and generates the response. In ASP.NET Core, the routing component is EndpointRoutingMiddleware; `app.UseRouting()` adds it to the pipeline. section 6.2 section 4.2.3

You usually do not need to call `UseRouting()` yourself: WebApplication adds routing and endpoint middleware by default. Add it explicitly when their position matters. For example, placing routing after static-file middleware lets static-file requests be handled first; placing authorization after routing lets it act on the selected endpoint. Middleware before routing cannot yet see that selection. section 6.5 section 13.1.2

A minimal API route

`app.MapGet("/", () => "Hello World!")` registers an endpoint; it does not add middleware. For a GET request to `/`, routing selects that endpoint, and endpoint middleware runs its handler. Middleware earlier in the pipeline can instead generate a response and stop the request before it reaches routing. section 3.7.2 section 4.2.3

Listing 14.1 Registering Razor Pages in Startup.Configure

WebApplicationBuilder builder = WebApplication.CreateBuilder(args);
 
builder.Services.AddRazorPages();    #1
 
var app = builder.Build();
 
app.UseStaticFiles();
app.UseRouting();                    #2
app.UseAuthorization();
 
app.MapRazorPages();                 #3
 
app.Run();

In this Razor Pages pipeline, `UseRouting()` follows static files and precedes authorization. `MapRazorPages()` registers the page endpoints that routing can select. section 14.1

How ASP.NET Core in Action, 3e covers it

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Pro ASP.NET Core 7, Tenth EditionRouting middleware is an ASP.NET Core request-pipeline component that matches requests to endpoints and stores the selected endpoint for later processing.

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Related concepts

request pipelineconfigures · A request pipeline is an ordered sequence of processing components through which HTTP requests and their responses pass in a web application.
routinguses · Routing is the selection of a path, destination, or processing component to direct an item, request, or flow toward an intended endpoint.
Razor Pagesuses · Razor Pages is an ASP.NET Core page-focused programming model in which independently addressable pages combine Razor markup with request-handling logic.
url pathuses · A URL path is the hierarchical component of a URL that identifies a resource or route within its host.
endpointuses · An endpoint is a network-accessible address or interface through which a service exposes a resource or operation and handles requests and responses.
handleruses · A handler is a callable or software component that processes an event, request, message, or other input and performs associated processing.

This explainer was generated by Manning's knowledge graph from the text of ASP.NET Core in Action, 3e. The section links point to the parts of the book it draws on.