Routing middleware matches an incoming request to an endpoint. In an explicit pipeline, `UseRouting()` selects a route; `UseEndpoints()` executes its endpoint to generate the response. Keeping those steps separate lets middleware between them inspect the selected endpoint before it runs. section 13.3.3 section 13.1.2
A route pairs a URL path pattern with an endpoint:
- `MapGet("routing", handler)` matches GET requests for `/routing`. Other mapping methods handle POST, PUT, DELETE, specified methods, or all methods. section 13.1.2
- `MapGet("capital/{country}", handler)` captures a path segment. The handler reads its value from `context.Request.RouteValues["country"]`. section 13.1.5
- An endpoint can be an asynchronous `RequestDelegate` that receives `HttpContext` and writes a response. section 13.1.2
Register and test a route
After building `app` in `Program.cs`, register `app.MapGet("routing", async context => { await context.Response.WriteAsync("Request Was Routed"); });`, then call `app.Run()`. Request `http://localhost:5000/routing` to see `Request Was Routed`. `WebApplication` accepts routes directly; ASP.NET Core can apply the routing setup automatically, even though routing middleware still performs the match. section 13.1.2 section 13.1.3
Pipeline configuration is not just cosmetic. With explicit `UseRouting()` and `UseEndpoints()`, an unmatched request can continue to later middleware; a matched endpoint handles the response. When switching to direct route registration, remove or reconsider a terminal middleware component: in the demonstrated configuration it runs for every request. The C# analyzer also warns when `UseEndpoints()` is used instead of top-level route registration. section 13.1.2 section 13.1.3
Inspect the selected endpoint
Place middleware between `UseRouting()` and `UseEndpoints()`, then call `context.GetEndpoint()`. A non-null result exposes the selected endpoint’s `DisplayName`, metadata, and request delegate. `WithDisplayName()` makes the selection easier to recognize in a response or diagnostic message. Changing it with `SetEndpoint()` is possible but calls for a compelling reason. section 13.3.3
Listing 13.5 Using the routing middleware in the Program.cs file in the Platform folder
using Platform;
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
app.UseMiddleware<Population>();
app.UseMiddleware<Capital>();
app.UseRouting();
#pragma warning disable ASP0014
app.UseEndpoints(endpoints => {
endpoints.MapGet("routing", async context => {
await context.Response.WriteAsync("Request Was Routed");
});
});
app.Run(async (context) => {
await context.Response.WriteAsync("Terminal Middleware Reached");
});
app.Run();
See a complete `Program.cs` pipeline with explicit routing, a GET endpoint, and terminal middleware for unmatched requests. section 13.1.2
