C# 4 and .NET 4

MVC ❘ 1267
At this point, hopefully, things should click into place. Prior to testing you added a controller called
ProductsController, which had a method called Index(), which at the time was described as being the
default controller method. Now you can deduce what actually happened when you entered the URL:
1. The routing system interpreted the URL entered and assigned values to controller, action, and id
as noted above.
2. ASP.NET MVC searched for — and found — a controller for Products (note that the URL didn’t need
to be /ProductsController, the Controller suffix is added automatically).
3. ASP.NET MVC searched for — and, again, found — an action called Index, which is the Index()
method in ProductsController.
4. When calling Index(), ASP.NET MVC searched for — and, you guessed it, found — a view in the
Products view folder capable of displaying a collection of Product objects.
5. ASP.NET rendered the view.
Similarly, when you subsequently attempted to view the details for an item, the appropriate method
(Details()) was located after interpreting the URL route /Products/Details/1. The final parameter here
was passed to the Details() method as an argument, although at this point things fell to pieces a bit as
that method is not yet implemented and no view was available.
This routing behavior, and the way that URLs are mapped directly to controller methods, is central to
understanding ASP.NET MVC. It means that you have a direct route from a given URL into your code, and what
you do in that code is, of course, entirely up to you. The “simple” operations, such as listing products and so on,
are therefore just the start of what is possible; you can write any action you can conceive of in the same way.
However, you must also consider other implications of this. You are in effect exposing your code, and the
parameters passed to your code, directly to users. This means that defensive coding is essential, as who
knows what parameters your methods might receive from people typing URLs manually.
action links
Now that you know how URLs are mapped to actions, it’s worth looking at how to include links in your
application. You could just hard-code a link in your site, for example, the following to get to the Products
page you added:
Products
However, this link makes assumptions about the site’s structure that aren’t necessarily permanent. If at
some point you were to change the routing specification this link would break.
Earlier in the chapter, you saw how the ASP.NET Routing system allows links to be dynamically generated
according to routing parameters. Similarly, ASP.NET MVC allows links to be generated according to the
controller, action, and additional values you want to use, as well as the text you want to display. This is
achieved through the Html.ActionLink() extension method, which has a number of overloads, depending
on what you want to achieve.
For example, if you look in the Site.Master master page file in the Views\Shared folder, you will see the
following code that defines the menu for the site:
code snippet PCSMVCMagicShop/Views/Shared/Site.Master
The overload used here has three string parameters, linkText, actionName, and controllerName.
The first parameter specifies the text to display, and the other two specify the action and controller to
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