Attribute Routing : Object reference not set to an instance of an object - asp.net-mvc

Question

I'm using this codes to Attribute Routing .
my controller :
[RouteArea("Administrator")]
[Route("{action}")]
public partial class HomeController : Controller
{
[HttpGet]
[Route("~/Home/Template/{id}")]
public virtual ActionResult Template(string template)
{
switch (template.ToLower())// error :Object reference not set to an instance of an object..
{
case "main":
return PartialView(Url.Content(MVC.Administrator.Home.Views.Main));
default:
throw new Exception("template not known");
}
}
}
RouteConfig :
internal static class RouteConfig
{
internal static void RegisterRoutes(AreaRegistrationContext context)
{
context.MapRoute(
"Administrator_default",
"Administrator/{controller}/{action}/{id}",
new { controller = "Home", action = "Index", id = UrlParameter.Optional },
namespaces: new[] { string.Format("{0}.Controllers", typeof(RouteConfig).Namespace) });
}
}
url : http://localhost:22738/home/template/main
how to use Attribute Routing ?
Is there a way to solve the problem? I have no idea

Answer 1

It would behoove you spend some time reading the documenation for attribute routing. See: http://blogs.msdn.com/b/webdev/archive/2013/10/17/attribute-routing-in-asp-net-mvc-5.aspx
First, you haven't enabled attribute routing. You need the following in RouteConfig.cs:
routes.MapMvcAttributeRoutes();
Second, you can't apply [Route] to a controller class. You can use [RoutePrefix] if that's what you're looking for. However, bear in mind, that if you include a param in your route prefix, all your action must accept that param. Although, since you have a param of action here, it's entirely possible that you just don't understand how this works. You don't pass the action name with attribute routing. The action that is hit is determined by the one that has the matching route.
Third, when you define a route on an action, you need only specify the portion of the route not covered by RouteArea or RoutePrefix. Using the tilde (~) says that you want to ignore all set prefixes and define the whole route for the action, if that's what you actually want here, that's fine, but just keep in mind that you don't have to follow the /Controller/Action/{id} convention employed by the default route in RouteConfig.cs. The whole point of attribute routing is to define custom routes easily. If you're going to rely on the default route, you might as well just use that and forget about attribute routing.
Finally, in your route, you're accepting the param, id, but your action doesn't take it. Instead it has its own param of template. The params need to match or either the route will not match or the action won't be able to work.
To summarize, the following is likely what you're looking for:
[RouteArea("Administrator")]
[RoutePrefix("home")]
public partial class HomeController : Controller
{
[Route("template/{template}")]
public virtual ActionResult Template(string template)
{
switch (template.ToLower())// error :Object reference not set to an instance of an object..
{
case "main":
return PartialView(Url.Content(MVC.Administrator.Home.Views.Main));
default:
throw new Exception("template not known");
}
}
}