Implementing default routes in VS .NET

Encoder Code 128 in VS .NET Implementing default routes

public class MvcApplication : HttpApplication { public static void RegisterRoutes(RouteCollection routes) { routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

routes.MapRoute( "Default", "{controller}/{action}/{id}", new { controller = "Home", action = "Index", id = UrlParameter.Optional } ); } protected void Application_Start() { RegisterRoutes(RouteTable.Routes); } }

In listing 16.2, the first operation is an IgnoreRoute B. We don t want Trace.axd, WebResource.axd, and other existing ASP.NET handlers routed through the MVC Framework, so the route {resource}.axd/{*pathInfo} ensures any request coming in with an extension of .axd won t be served by ASP.NET MVC. The second operation defines our first route. Routes are defined by calling MapRoute on a RouteCollection C, which adds a Route object to the collection. So, what comprises a route A route has a name, a URL pattern, default values, and constraints. The latter two are optional, but you ll most likely use default values in your routes. The route in listing 16.2 is named Default, has a URL pattern of {controller}/{action}/{id}, and includes a default value dictionary that identifies the default controller and action. These default values are specified in an anonymous type, which was introduced in .NET 3.5 and carries forward into .NET 4. If we pick apart this route, we can easily see its components: the first segment of the URL will be treated as the controller, the second segment as the action, and the third segment as the ID. Notice how these values are surrounded in curly braces. When a URL comes in with the following format, what do you think the values will be for controller, action, and ID

http://example.com/users/edit/5

Figure 16.3 shows how the values are pulled out of the URL. Remember, controller id this is only the default route template. You re free to change this for your own applications. http://example.com/users/edit/5 The route values, shown in action table 16.2, are all strings. The controller will be extracted out of this Figure 16.3 Decomposing a URL into route values using URL as users. The controller part the default route of {controller}/{action}/{id} of the class name is implied by convention, so the controller class created will be UsersController. As you can probably already tell, routes aren t case sensitive. The action describes the name of the method to call on our controller. In ASP.NET MVC, an action is defined as a public method on a controller that returns an

"users" "edit" "5"

specified controller that matches the name supplied for the action. If none is found, it will also look for a method that has the ActionNameAttribute applied with the specified action. The remaining values defined in a route are pumped into the action method as parameters, or left in the Request.Params collection if no method parameters match. Notice that the ID is also a string, but if your action parameter is defined as an integer, a conversion will be done for you. Listing 16.3 shows the action method that will be invoked as a result of the URL in figure 16.3.

Listing 16.3 An action method matching http://example.com/users/edit/5

public class UsersController : Controller { public ActionResult Edit(int id) { return View(); } }

What happens if we omit the ID or action from our URL What will the URL http:// example.com/users match To understand this, we have to look at the route defaults. In our basic route defined in listing 16.2, we can see that our defaults are defined as

new { controller = "Home", action = "Index", id = UrlParameter.IOptional }

This allows the value of "Index" to be assumed when the value for action is omitted in a request that matches this route. You can assign a default value for any parameter in your route. We can see that the default routes are designed to give a reasonable level of functionality for an average application, but in almost any real-world application you want to design and customize a new URL schema. In the next section, we ll design a URL schema using custom static and dynamic routes.