ASP.NET MVC- Controllers and Routing- Routing

二、Creating Custom Routes

　　In this tutorial, you learn how to  add a custom route to an ASP.NET MVC application. You learn how to modify  the default route table in the Global.asax file with a custom route.

　　For many simple ASP.NET MVC applications,  the default route table will work just fine. However, you might discover  that you have specialized routing needs. In that case, you can create  a custom route.

　　Imagine, for example, that you are  building a blog application. You might want to handle incoming requests  that look like this:

/Archive/12-25-2009

　　When a user enters this request, you  want to return the blog entry that corresponds to the date 12/25/2009.  In order to handle this type of request, you need to create a custom  route.

　　The Global.asax file in Listing 1 contains  a new custom route, named Blog, which handles requests that look like  /Archive/entry date.

　　Listing 1  - Global.asax (with custom route)

using System.Web.Mvc;
using System.Web.Routing;
namespace MvcApplication1
{
    public class MvcApplication : System.Web.HttpApplication
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
            routes.MapRoute(
                "Blog",                                           // Route name
                "Archive/{entryDate}",                            // URL with parameters
                new { controller = "Archive", action = "Entry" }  // Parameter defaults
            );
            routes.MapRoute(
                "Default",                                              // Route name
                "{controller}/{action}/{id}",                           // URL with parameters
                new { controller = "Home", action = "Index", id = "" }  // Parameter defaults
            );
        }
        protected void Application_Start()
        {
            RegisterRoutes(RouteTable.Routes);
        }
    }
}

　　The order of the routes that you add  to the route table is important. Our new custom Blog route is added  before the existing Default route. If you reversed the order, then the  Default route always will get called instead of the custom route.

　　The custom Blog route matches any request  that starts with /Archive/. So, it matches all of the following URLs:

　　/Archive/12-25-2009

　　/Archive/10-6-2004

　　/Archive/apple

　　The custom route maps the incoming  request to a controller named Archive and invokes the Entry() action.  When the Entry() method is called, the entry date is passed as a parameter  named entryDate.

　　You can use the Blog custom route with  the controller in Listing 2.

Listing 2 - ArchiveController.cs

using System;
using System.Web.Mvc;
namespace MvcApplication1.Controllers
{
    public class ArchiveController : Controller
    {
        public string Entry(DateTime entryDate)
        {
            return "You requested the entry from " + entryDate.ToString();
        }
    }
}

　　Notice that the Entry() method in Listing  2 accepts a parameter of type DateTime. The MVC framework is smart enough  to convert the entry date from the URL into a DateTime value automatically.  If the entry date parameter from the URL cannot be converted to a DateTime,  an error is raised (see Figure 1).

Figure 1 - Error from converting parameter

　　Summary

　　The goal of this tutorial was to demonstrate  how you can create a custom route. You learned how to add a custom route  to the route table in the Global.asax file that represents blog entries.  We discussed how to map requests for blog entries to a controller named  ArchiveController and a controller action named Entry().

三、Creating a Route Constraint

　　In this tutorial, Stephen Walther demonstrates how you can control how browser requests match routes by creating route constraints with regular expressions.
　　You use route constraints to restrict  the browser requests that match a particular route. You can use a regular  expression to specify a route constraint.

　　For example, imagine that you have  defined the route in Listing 1 in your Global.asax file.

　　Listing 1  - Global.asax.cs

routes.MapRoute(
    "Product",
    "Product/{productId}",
    new {controller="Product", action="Details"}
);

　　Listing 1 contains a route named Product.

　　You can use the Product route to map browser requests to the ProductController  contained in Listing 2.

　　Listing 2  - Controllers\ProductController.cs

using System.Web.Mvc;
namespace MvcApplication1.Controllers
{
    public class ProductController : Controller
    {
        public ActionResult Details(int productId)
        {
            return View();
        }
    }
}

　　Notice that the Details() action exposed  by the Product controller accepts a single parameter named productId.  This parameter is an integer parameter.

　　The route defined in Listing 1 will  match any of the following URLs:

• /Product/23
• /Product/7

　　Unfortunately, the route will also  match the following URLs:

• /Product/blah
• /Product/apple

　　Because the Details() action expects  an integer parameter, making a request that contains something other  than an integer value will cause an error. For example, if you type  the URL /Product/apple into your browser then you will get the error  page in Figure 1.

　　What you really want to do is only  match URLs that contain a proper integer productId. You can use a constraint  when defining a route to restrict the URLs that match the route. The  modified Product route in Listing 3 contains a regular expression constraint  that only matches integers.

Listing 3 - Global.asax.cs

routes.MapRoute(
    "Product",
    "Product/{productId}",
    new {controller="Product", action="Details"},
    new {productId = @"\d+" }
 );

　　

　　The regular expression \d+ matches  one or more integers. This constraint causes the Product route to match  the following URLs:

• /Product/3
• /Product/8999

　　But not the following URLs:

• /Product/apple
• /Product

　　These browser requests will be  handled by another route or, if there are no matching routes, a The  resource could not be found error will be returned.

四、Creating a Custom Route Constraint

　　Stephen Walther demonstrates how you can create a custom route constraint. We implement a simple custom constraint that prevents a route from being matched when a browser request is made from a remote computer.

　　The goal of this tutorial is to demonstrate  how you can create a custom route constraint. A custom route constraint  enables you to prevent a route from being matched unless some custom  condition is matched.

　　In this tutorial, we create a Localhost  route constraint. The Localhost route constraint only matches requests  made from the local computer. Remote requests from across the Internet  are not matched.

　　You implement a custom route constraint  by implementing the IRouteConstraint interface. This is an extremely  simple interface which describes a single method:

bool Match(
    HttpContextBase httpContext,
    Route route,
    string parameterName,
    RouteValueDictionary values,
    RouteDirection routeDirection
)

　　The method returns a Boolean value.  If you return false, the route associated with the constraint won’t  match the browser request.The Localhost constraint is contained  in Listing 1.

　　Listing 1 - LocalhostConstraint.cs

using System.Web;
using System.Web.Routing;
namespace MvcApplication1.Constraints
{
    public class LocalhostConstraint : IRouteConstraint
    {
        public bool Match
            (
                HttpContextBase httpContext,
                Route route,
                string parameterName,
                RouteValueDictionary values,
                RouteDirection routeDirection
            )
        {
            return httpContext.Request.IsLocal;
        }
    }
}

　　The constraint in Listing 1 takes advantage  of the IsLocal property exposed by the HttpRequest class. This property  returns true when the IP address of the request is either 127.0.0.1  or when the IP of the request is the same as the server’s IP address.

　　You use a custom constraint within  a route defined in the Global.asax file. The Global.asax file in Listing  2 uses the Localhost constraint to prevent anyone from requesting an  Admin page unless they make the request from the local server. For example,  a request for /Admin/DeleteAll will fail when made from a remote server.

　　Listing 2 - Global.asax

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;
using MvcApplication1.Constraints;
namespace MvcApplication1
{
    public class MvcApplication : System.Web.HttpApplication
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
            routes.MapRoute(
                "Admin",
                "Admin/{action}",
                new {controller="Admin"},
                new {isLocal=new LocalhostConstraint()}
            );
            //routes.MapRoute(
            //    "Default",                                              // Route name
            //    "{controller}/{action}/{id}",                           // URL with parameters
            //    new { controller = "Home", action = "Index", id = "" }  // Parameter defaults
            //);
        }
        protected void Application_Start()
        {
            RegisterRoutes(RouteTable.Routes);
        }
    }
}

　　The Localhost constraint is used in  the definition of the Admin route. This route won’t be matched by  a remote browser request. Realize, however, that other routes defined  in Global.asax might match the same request. It is important to understand  that a constraint prevents a particular route from matching a request  and not all routes defined in the Global.asax file.

　　Notice that the Default route has been  commented out from the Global.asax file in Listing 2. If you include  the Default route, then the Default route would match requests for the  Admin controller. In that case, remote users could still invoke actions  of the Admin controller even though their requests wouldn’t match  the Admin route.

原文：http://www.asp.net/mvc/tutorials/controllers-and-routing/asp-net-mvc-controller-overview-vb

译文：http://www.cnblogs.com/JimmyZhang/archive/2009/03/08/1406512.html