9. [Updated] - ASP .Net core - Fundamentals - Routing

 This series is a collection of knowledge about ASP .NET Core. It just is my notes.

Part 1: Startup file.

Part 2: DI.

Part 3: Middleware.

Part 4: Host and Servers.

Part 5: Configurations.

Part 6: Environment.

Part 7: Logs.

Part 8: Error Handling.

Part 10: Make an HTTP Request.

Part 11: Static files.

Part 12: Authentication and Authorization.

Part 13: CORS.

• Routing is responsible for matching incoming HTTP requests and dispatching those requests to the app's executable endpoints
• How to use - [From ASP. Net Core 3.0]

public void Configure(IApplicationBuilder app)

{

    app.UseStaticFiles();

    // Add the EndpointRoutingMiddleware

    app.UseRouting();

    // All middleware between UseRouting and UseEndpoints will know which endpoint will be invoked

    // can be benerfits from it to do some logical checks

    // For instances:

    app.UseCors();

    app.UseAuthentication();

    app.UseAuthorization();

    // Execute the endpoint selected by the routing middleware

    app.UseEndpoints(endpoints =>

    {

        endpoints.MapDefaultControllerRoute();

    });

}

From "UseRouting" to "UseEndpoints" is called Routing zone, some highlighted points:

• The endpoint is always null before UseRouting is called.
• If a match is found, the endpoint is non-null between UseRouting and UseEndpoints.
• The UseEndpoints middleware is terminal when a match is found.
• The middleware after UseEndpoints execute only when no match is found.

• Endpoint routing

            You can attach metadata to endpoints so intermediate middleware (e.g. Authorization, CORS) can know what will be eventually executed For example: MapHealthChecks

app.UseAuthentication();

app.UseAuthorization();

app.MapHealthChecks("/healthz").RequireAuthorization();

How to create a endpoint routing aware:

• Write an extension method on IEndpointRouteBuilder.
• Create a nested middleware pipeline using CreateApplicationBuilder.
• Attach the middleware to the new pipeline.
• Build the middleware pipeline into a RequestDelegate.
• Call Map and provide the new middleware pipeline.
• Return the builder object provided by Map from the extension method.

Code sample

References:

[Microsoft Learn] - Routing in ASP.NET Core