What is ASP.Net MVC Routing and why is it needed, explained.

Introduction : The ASP.Net Routing framework is at the core of every ASP.Net MVC request and it is simply a pattern-matching system. At the application start-up it registers one or more patterns with route table of the framework to tell it what to do with the pattern matching requests. For routing main purpose is to map URLs to a particular action in a specific controller.

When the routing engine receives any request it first matches the request URL with the patterns already registered with it. If it finds any matching pattern in route table it forwards the request to the appropriate handler for the request. If the request URL does not matches with any of the registered route patterns the routing engine returns a 404 HTTP status code.

Where to configure :
Global asax

How to configure :
ASP.Net MVC routes are responsible for determining which controller methods to be executed for the requested URL. The properties for this to be configured are :-

Unique Name : A name unique to a specific route.
URL Pattern : A simple URL pattern syntax.
Defaults : An optional set of default values for each segments defined in URL pattern.
Constraints : A set of constraints to more narrowing the URL pattern to match more exactly.

The RegisterRoute method in RouteConfig.cs file :-
    public class RouteConfig
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); // ignore route with extension .axd

            routes.MapRoute(
                name: "Default", // Name of the route
                url: "{controller}/{action}/{id}", // pattern for the url
                defaults: new { controller = "Login", action = "Index", id = UrlParameter.Optional } // default values                 for each section
            );
        }

    }

Then in Global.asax.cs file call this on application start event handler so that this will be registered on application start itself :-

protected void Application_Start()
{
     RouteConfig.RegisterRoutes(RouteTable.Routes);

}

How Routing engine Works :-

Route Matching :-

Hope this will give a clear understanding on what is routing and how routing engine works ....

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