MVC Routes

MVC3 gives you great control over how URLs are mapped to your controllers. It gives you the ability to define your URLs in a human readable SEO (Search Engine Optimization) friendly fashion, to remap old URLs to new functionality and side-by-side utilize classic ASP.NET sites inside of MVC3. It also results in hiding what kind of page user is calling and what environment we are working in. Most of the new websites are following this and it is important to understand that routing is not URL rewriting as routing will have customizations and many attachments towards request/response.
When we create any type of MVC application by default GLOBAL.ASAX file is created becoz ASP.NET implements MVC using this global application class mainly. Routes defined in the Global.asax.cs file of our MVC3 web application/site. In this global.asax file most important element relative to our work is RegisterRoutes method. By default, there is only one route defined in the RegisterRoutes method that looks like the line below.
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
);
This route defines the route name, which can be anything as long as it is unique, the URL template, and the parameter defaults. The default route that is pre-defined for you maps to Controller/Action/id. You can add additional routes by copying the same line and adjusting the URL parameters and the related default values. Remember when we add additional routes the order is important.
Custom MVC3 Routes
One of the many factors frequently considered by search engines to determine the relevance of a particular page to a particular search term is whether or not the URL link itself includes a particular term. In a classic ASP.NET site for a magazine, you might have a URL that looks like www.internet.com/ViewArticle.aspx?id=123. This URL passes the ID number of the article to view, but the URL itself doesn't describe the content in any human readable way. If the URL instead was www.internet.com/MVC3_Routing/123 a human-or a web crawler-could read that and know that the article is about MVC3 Routing.
Another frequent use of custom routing is to allow multiple sites to link to the same location while providing additional data about where they came from. For example, if you had a link to a product page and you wanted to provide custom co-branding based on which one of your partners linked in to a page, you could do so by including a "partner name" variable in the link. A link like this could be to www.internet.com/PartnerA/Article/123 or www.internet.com/PartnerB/Article/123 for example. This would allow two different sites to link to the same article while providing their own information in the process.
The code block below defines a new route called ArticleRoute that defines a new parameter called article in addition to the standard controller and action.
routes.MapRoute(
"ArticleRoute",
"{article}/{controller}/{action}",
new { article="Unknown", controller = "Home", action = "Index" } );
You can access this custom article part of the route in your controller by accessing the RouteData object.
RouteData.Values["article"]
To access the RouteData object in your Razor views, use the @Url.RequestContext.RouteData object.
When you are constructing URLs that use string data such as article titles or author's names, you will need to use some form of URL-friendly encoding. The easiest method is to use HttpUtility.UrlEncode("Your String") which will replace all of the URL unfriendly characters with the appropriate HTML escapes.B This method is web spider friendly but not necessarily human readable URL friendly.
It is very important to remember that any data in a URL is easily user manipulated and shouldn't be trusted. It is not an appropriate place to pass application variables between pages unless they are of a nature that it would be acceptable if the user manipulated them.
Re-mapping Routes
From time to time it is necessary to re-route an old URL to a new location. Traditionally you would use a redirect page to let users know to update their bookmarks and include a link to the new location. Sometimes it is impractical or even impossible to change URLs as is the case when you have 3rd party software systems set up to access and scrape particular URLs.
If you wanted to route MyRazor.cshtml page to your MVC3 Home/Index controller, you can do so by defining a route like the one below.
routes.MapRoute("RT", " MyRazor.cshtml ",
new { controller = "OtherController", action = "Packed" });
Including Classic ASP.NET as a Sub-directory in an MVC3 Web Application
If you have a large classic ASP.NET web site that you need to incrementally transition to MVC3 you can put the entire classic ASP.NET web site in your MVC3 web site as a sub-directory. You can then call the IgnoreRoute method seen in the code block below to tell MVC3 to not handle that particular URL path.
routes.IgnoreRoute("OldClassicASP/");
Constraints
You can define additional constraints to your defined routes to insure that the values passed for particular parts of your route are valid. This is useful not only for general security related needs but is also useful for scenarios where you might want to have additional routing logic in place for particular routes.
routes.MapRoute(
"ColorPath", // Route name
"{color}/{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
, new { color="blue" }
);
In the example route above, a new anonymous object is added to the MapRoute path call that adds a constraint to this path. The route will only be used if the color is blue.
Namespaces
In large ASP.NET MVC3 applications you can potentially have hundreds of controllers. This can become problematic because the .NET Framework looks in the Controllers folder and all sub-folders looking for controllers to match up with the defined routes.
To help you organize your code, you can add namespaces to your routes to constrain the controllers the route will match to particular namespaces. The route below will only use controllers defined in the Home.Guru namespace.
routes.MapRoute("NamespacedRoute", "Cool/{controller}/{action}",
new { controller = "Home", action = "Index", id = UrlParameter.Optional } , null,
, new string[] { "Home.Guru" });
Global Filters
If you want to define code that runs before or after your routing calls, you can define a global filter. Global filters are registered in the Global.asax.cs file by adding a line to the RegisterGlobalFilters method. This method, by default, registers the HandleErrorAttribute that is used to handle error conditions in ASP.NET MVC3 applications.
If you wanted to add a copyright notice at the bottom of all of your pages, you could add a global filter attribute that overrides the OnResultExecuted method which is run after your page has run.
public class CopyrightNoticeAttribute : ActionFilterAttribute
{
public override void OnResultExecuted(ResultExecutedContext filterContext)
{
filterContext.HttpContext.Response.Write(String.Format("<h1>Copyright {0}</h1>",DateTime.Now.Year));
}
}
Once your custom attribute has been written you can add it to the global.asax.cs file.
public static void RegisterGlobalFilters(GlobalFilterCollection filters)
{
filters.Add(new CopyrightNoticeAttribute());
filters.Add(new HandleErrorAttribute());//Default in MVC3
}

------------------*--------------------------*-----------------------------------*-------------------------

Routing in ASP.NET MVC 3 Tutorial

Q) What is ASP.NET MVC Routing?

Answer: When request is received from the browser, it is routed to URL routing module object which transfers request to the MVCHttpHandler. The MVCHttpHandler is responsible to Map incoming request with controller [by adding suffix controller to the controller value], action and Parameter to action if any. Parameters to action are optional. ASP.NET URL pattern consists of literal and placeholders where placeholders are separated by '/' and defined by {placeholder name}. This process works like dictionary where keys are the placeholder names defined in the URL pattern, and the values are in the URL.

E.g. Let URL be www.myshop.com\products\show\cosmatics

Keys are {controller}/{action}/{id} and their values are products/show/cosmatics

To understand the MVC Application Execution Process, please refer to the following MSDN article.

• http://msdn.microsoft.com/en-us/library/dd381612(v=vs.100).aspx

Route table: Route table gets created in the global.asax. The Global.asax file, also known as the ASP.NET application file. Global.asax contains code for responding to application-level events raised by ASP.NET or byHttpModules. The route table is created during the Application Start event.

Consider the following URL:

• http://localhost/home/index

We are targeting home controller and index action.This is defined by adding an entry in to the "routes" collection using the "maproute" function.

Let's have a look at the register route function in the Global.asax.

public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
    routes.MapRoute(
                "Default", // Route name
                "{controller}/{action}/{id}", // URL with parameters
                new { controller = "Home", action = "Index", 
                id = UrlParameter.Optional } // Parameter defaults
    );
} 

routes.MapRoute(string name,string url,object default) function takes 3 arguments:

1. Route name
2. URL with parameter
3. Object of class containing default parameter values

Q) How to create Custom Route?

All the mapped routes are stored as RouteCollection in the Routes property of the RouteTable class. You can add multiple entries of the route in the route collection by defining unique route name for each key.

public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
    routes.MapRoute(
                "Default", // Route name
                "{controller}/{action}/{id}", // URL with parameters
                new { controller = "Home", action = "Index", 
                id = UrlParameter.Optional } // Parameter defaults
    );
    routes.MapRoute(
                "Home", // Route name
                "{controller}/{action}/{id}", // URL with parameters
                new { controller = "Home", action = "Index1", 
                id = UrlParameter.Optional } // Parameter defaults
    );
} 

The sequence of the MapRoute is important. In our case, route name "Default" gets executed by default as it is before the route name "Home". If you look at the controller class, it contains the suffix name "Controller" to it, but you do not need to specify suffix controller to the URL as MVC routing engine will add suffix "Controller" to controller name by default.

Q) How to Add Constraint to the Route?

Constraints are the rule enforced on the parameter value of the URL. If the parameter values are not inline with the constraint for a route is not handled by the URL routing engine. You can add the constraint to the URL route based on your application requirement. Similar to the custom routes constraint can be added in the MapRoute function as argument. Constraints are defined by using regular expressions or by using objects that implement theIRouteConstraint interface.

Using regular expression: Consider URL http://localhost/home/index/id, constraint to id variable that it should accept number only. We can apply regular expression as argument to the MapRoute function overload that accepts constraint as the object. MapRoute(string name,string url,object default,object constraint), the application requirement is to add:

routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", 
id = "id" } // Parameter defaults
, new { id = @"\d+" } //Constraint
);

id = @"\d+" regular expression enforces rule to accept number value of id variable. Route that contains id value other than the number is result into HTTP 404 page not found error.

You can get more information about regular expression in the following MSDN article.

• http://msdn.microsoft.com/en-us/library/ms972966.aspx

Using object that implements the IRouteConstraint, consider URL http://localhost/home/index/idconstraint to id variable that it should accept Date only. Let's create a class that implements the IRouteConstraint.IRouteConstraint in force to use method Match having the following signature, the application requirement is to add:

public class CustomContraint : IRouteConstraint
{ 
    #region IRouteConstraint Members
    public bool Match(HttpContextBase httpContext, Route route, 
    string parameterName, RouteValueDictionary values, RouteDirection routeDirection)
    {
        throw new NotImplementedException();
    }
    #endregion
}

Let's add logic that validates parameterName id with date value only.

public class CustomContraint : IRouteConstraint
{
    public bool Match(HttpContextBase httpContext, Route route, 
    string parameterName, RouteValueDictionary values, RouteDirection routeDirection)
    {
        DateTime dt;
        bool result = DateTime.TryParseExact(values["id"].ToString(),
        "yyyyMMdd", CultureInfo.InvariantCulture, DateTimeStyles.None, out dt);
        return result;
    }
} 

Let's create an object of Class that implements IRouteConstraint and pass to the MapRoute function overload that accepts the constraint object.

routes.MapRoute(
    "Home", // Route name
    "Home/Index1/{id}", // URL with parameters
    new { id = DateTime.Now }, // Parameter defaults
    new { isLocal = new CustomContraint() } //Constraint
);  

New CustomContraint() objects implement the IRouteConstraint interface.