MSDN Magazine - March 2008 - (Page 45)

Hello, Controller instance, called the HiThere method, and passed Chris as the value of the ID parameter. This default route gives you a lot, but you can add your own routes as well. For example, I want a really friendly site where folks should only have to enter their name for a personalized greeting. If I add this route to the top of the routing table RouteTable.Routes.Add(new Route { Url = “[id]”, Defaults = new { controller = “Hello”, action = “HiThere” }, RouteHandler = typeof(MvcRouteHandler) }); Several things should leap out at you. There are no runat=“server” tags. There’s no form tag. There are no control declarations. In fact, this looks a lot more like classic ASP than ASP.NET. Note that MVC views are only responsible for generating output, so they don’t need any of the event handling or complex controls that Web Forms pages do. The MVC Framework does borrow the .aspx file format as a useful text templating language. You can even use codebehind if you want, but by default the Figure 4 Adding a View to codebehind file looks like this: using System; using System.Web; using System.Web.Mvc; namespace HelloFromMVC.Views.Hello { public partial class HiThere : ViewPage { } } the Project I can then simply go to http://localhost/Chris and my action is still invoked, and I see my familiar friendly greeting. How did the system know which controller and action to invoke? The answer is in the Defaults parameter. This makes use of the new C# 3.0 anonymous type syntax to create a pseudo dictionary. The Defaults object on the Route can contain arbitrary extra information, but for MVC it can also contain some well-known entries: controller and action. If there’s no controller or action specified in the URL, then it’ll use the name in the Defaults. That’s why I can No page Init or load methods, no event handlers, nothing except the declaration of the base class, which is not Page but instead ViewPage. This is all you need to be an MVC view. Run the app, navigate to http://localhost: /Hello/HiThere/Chris, and you’ll see something like Figure 5. If, instead of Figure 5, you see a nasty looking exception, don’t panic. If you have the HiThere.aspx file set as the active document in Visual Studio when you press F5, Visual Studio will attempt to access the .aspx file directly. Since MVC views require the controller to have run before displaying, trying to navigate directly to the page will not work. Just edit the URL to match what you see in Figure 5, and it should work fine. How’d the MVC Framework know to call my action method? There wasn’t even a file extension for that URL. The answer is URL routing. If you look inside the global.asax.cs file, you’ll see the chunk of code in Figure 6. The global RouteTable stores a collection of Route objects. Each Route describes a URL form and what to do with it. By default, two routes get added to the table. The first is what does the magic. It says that for each URL that consists of three parts after the server name, the first part should be taken as a controller name, the second as an action name, and the third as the ID parameter: Url = “[controller]/[action]/[id]” Figure 5 Successful MVC View Figure 6 Route Table public class Global : System.Web.HttpApplication { protected void Application_Start(object sender, EventArgs e) { // Change Url= to Url=”[controller].mvc/[action]/[id]” // to enable automatic support on IIS6 RouteTable.Routes.Add(new Route { Url = “[controller]/[action]/[id]”, Defaults = new { action = “Index”, id = (string)null }, RouteHandler = typeof(MvcRouteHandler) }); RouteTable.Routes.Add(new Route { Url = “Default.aspx”, Defaults = new { controller = “Home”, action = “Index”, id = (string)null }, RouteHandler = typeof(MvcRouteHandler) }); This default route is what enabled my HiThere method to get invoked. Remember this URL: http://localhost/Hello/HiThere/Chris? This route mapped Hello to the controller, HiThere to the action, and Chris to the ID. The MVC Framework then created a Hello- } } ASP.NET MVC march2008 45

Table of Contents Feed for the Digital Edition of MSDN Magazine - March 2008

MSDN Magazine - March 2008 Contents Toolbox CLR Inside Out Data Points Advanced Basics Office Space Introducing ASP.NET MVC Loosen Up CI Server Performance Office Development Test Run Security Briefs Extreme ASP.NET Foundations .NET Matters {End Bracket}

MSDN Magazine - March 2008

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