ASP.NET Routing is a fundamental feature of every ASP.NET MVC application, responsible for mapping incoming browser requests to specific controller actions. The routing mechanism allows developers to define user-friendly URLs and provides a way to handle various types of URL patterns.
In an ASP.NET MVC application, ASP.NET Routing is enabled in the Web.config file, where four sections (system.web.httpModules, system.web.httpHandlers, system.webserver.modules, and system.webserver.handlers) are relevant to routing. Additionally, a route table is created in the Global.asax file during the Application Start event.
The default route table typically includes a single route named “Default,” which maps the first segment of a URL to a controller name, the second segment to a controller action, and the third segment to an optional parameter named “id.” The default route includes parameter defaults, ensuring seamless execution even when certain segments are missing in the URL.
Throughout the application’s lifecycle, the Application_Start() method is called, which, in turn, invokes the RegisterRoutes() method to create and register the route table.
Routing in ASP.NET Core is the process of matching incoming HTTP requests to the appropriate controller and action methods. It plays a crucial role in determining how URLs are structured and how requests are handled. By defining routes, developers can create user-friendly URLs and enable a clear separation of concerns in their applications, making it easier to maintain and extend the codebase.
ASP.NET Core routing is based on the concept of route templates, which define the URL patterns that incoming requests should match. Route templates consist of placeholders for controller, action, and other parameters, allowing dynamic URL segments. Routes can be registered in the application’s startup configuration, and they are processed in the order they are added, with the first matching route being used to handle the request.
Route templates use placeholders enclosed in curly braces, such as “{controller}” and “{action}”, to define the URL structure. These placeholders are replaced with the appropriate values during request processing. Additional route parameters can be added using placeholders like “{id}” or custom names. Route templates are essential in creating concise and meaningful URLs that align with the application’s design and architecture.
Route constraints in ASP.NET Core are used to restrict the values that can be matched by a route parameter. Constraints are applied using regular expressions or predefined constraints like “int” or “bool”. By using constraints, developers can control the format and content of the route parameters, ensuring that only valid values are accepted and processed. This enhances the security and reliability of the application’s routing mechanism.