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Validate url in routing level itself in ASP.NET MVC

How to validate the data passed in url at the routing level itself in ASP.NET MVC?

Apart from Model validation, custom validation and other validations we have seen, the data can also be validated at the route level itself when any segment variables data is passed in the url.

Let’s assume that we have to restrict a certain URL pattern for those controllers whose name starts with “R”, we can specify below routes.

/APP_START/ROUTECONFIG.CS

// goes to the url, when the controller starts with R
            routes.MapRoute("ConstrainRouteR",
"{controller}/{action}/{id}/{*catchall}",
                new { controller = "RoutingStuffs", action = "Index", id =
UrlParameter.Optional },
                new { controller = "^R.*" });

Notice the 4^th parameter in above code that is the constraint parameter to specify. This instructs that if the controller name starts with “R” then only this route is used to serve the request. (Note that default route mechanism doesn’t need to be removed).

• http://localhost:63087/RoutingStuffs/CatchAll/155/something url works provided we have CatchAll method in the RoutingStuffs controller

• http://localhost:63087/Home/CatchAll/155/something doesn’t work as the controller name doesn’t start with “R”.

ACTION METHOD IN BOTH CONTROLLER 

(RoutingStuffsController.cs and HomeController.cs)

public ActionResult CatchAll(string id = null, string catchall = null)
{
       return View();
}

Similarly, we can also restrict the action method of a specific controller by specifying below route config.

// goes to the url, when the controller starts with R and action is either Index or
About
            routes.MapRoute("ConstrainRouteRA",
"{controller}/{action}/{id}/{*catchall}",
                new { controller = "RoutingStuffs", action = "Index", id =
UrlParameter.Optional },
                new { controller = "^R.*", action = "^Index$|^About$" });

Restricting a request type either GET or POST.

// Constraining a route using HTTP method
            routes.MapRoute("ConstraintRouteHttp",
"{controller}/{action}/{id}/{*catchall}",
                new { controller = "RoutingStuffs", action = "Index", id =
UrlParameter.Optional },
                new { controller = "RoutingStuffs", action = "Index|About",
httpMethod = new HttpMethodConstraint("GET", "POST") });

Restricting a request whose controller starts with H, action method is either Index or About and Id segment value is in between 10 and 20.

// Range routes constraint
            // controller starts with H, action is either Index or About, request
typen is GET and Id value is in between 10 and 20
            routes.MapRoute("ConstraintRouteRange",
"{controller}/{action}/{id}/{*catchall}",
                 new { controller = "RoutingStuffs", action = "Index", id =
UrlParameter.Optional },
                 new
                 {
                     controller = "^H.*",
                     action = "Index|About",
                     httpMethod = new HttpMethodConstraint("GET"),
                     id = new RangeRouteConstraint(10, 20)
                 });

In this case, we might need to comment the default route that comes with project template so that it doesn’t conflict with this.

• http://localhost:63087/Home/Index/155 doesn’t work as Id segment value is 155 not between 10 and 20.
• http://localhost:63087/Home/Index/15 work as the Id segment value is in between 10 and 20.