Routing Cycle in .NetCore

In ASP.NET Core, the request routing cycle is a process that directs incoming HTTP requests to the appropriate action methods of controllers or endpoints. Routing is a critical feature that defines how a URL maps to a specific piece of code in the application. Let's break down the routing cycle and how it works in .NET Core:

Overview of the Routing Cycle in ASP.NET Core

1. Request Initiation

   • A client (e.g., browser, Postman) sends an HTTP request to the server.
   • The ASP.NET Core application receives the request, and the routing middleware determines which endpoint should handle it.
     

2. Routing Middleware

   • The request is processed by the routing middleware, which is added to the middleware pipeline in Startup.cs or Program.cs.
   • The routing middleware analyzes the URL and matches it against defined routes in the application.
   • If a match is found, the middleware assigns routing information to the request context.
     

3. Endpoint Matching

   • After the middleware identifies a matching route, it maps the request to an appropriate endpoint (e.g., a controller action or a Razor Page).
   • If a corresponding endpoint is not found, the middleware will return a 404 (Not Found) response.
     

4. Controller Selection

   • If the route matches a controller, the framework instantiates the controller class and looks for an action method that matches the HTTP request (based on the method name, HTTP verbs like GET or POST, and route parameters).
     

5. Action Execution

   • Once the appropriate controller and action method are determined, the action method is executed.
   • The action method can process the request data, interact with services (e.g., databases), and return a response.
     

6. Result Execution

   • The action method typically returns an IActionResult, which could be a ViewResult, JsonResult, or RedirectResult.
   • The result is then rendered and sent back to the client as an HTTP response.