With MvcCodeRouting, URL generation is relative to the current route (the route that matched the current HTTP request). That means that when you do Url.Action("Foo", "Bar"), the Bar controller must be in the same Route Context as the current executing controller.
Route Context is the concept that MvcCodeRouting uses to define a hierarchy of routes, and in consequence a hierarchy of controllers. Controllers that share the same route context are considered siblings when it comes to matching routes for URL generation. This means that no special syntax is required to refer to other sibling controllers. Usually, controllers in the same namespace are also in the same route context, except for default controllers, which are in the route context of their parent namespace. For example:
| Controller | Route Context |
|---|---|
| MyStore.Controllers.HomeController | (empty) |
| MyStore.Controllers.UserController | (empty) |
| MyStore.Controllers.Admin.AdminController | (empty, default controller) |
| MyStore.Controllers.Admin.UserController | Admin |
| MyStore.Controllers.Admin.ProductController | Admin |
| MyStore.Controllers.Admin.Product.CategoryController | Admin/Product |
Asuming MyStore.Controllers.HomeController is the root controller, what controller does Url.Action("", "User") link to? it depends on the current executing controller; if it's HomeController then it links to UserController; if it's Admin.ProductController then it links to Admin.UserController.
MvcCodeRouting recognizes a special controller reference syntax that you can use to link to controllers in a different route context than the current executing controller.
| Reference name | Example code | Current controller | Returns |
|---|---|---|---|
| Sibling or self | Url.Action("", "User") |
HomeController | /User |
| Child or child of sibling | Url.Action("", "Admin.User") |
HomeController | /Admin/User |
| Child | Url.Action("", "+User") |
Admin.AdminController | /Admin/User |
| Grandchild | Url.Action("", "+Product.Category") |
Admin.AdminController | /Admin/Product/Category |
| Parent | Url.Action("", "..") |
Admin.UserController | /Admin |
| Sibling of parent | Url.Action("", "..User") |
Admin.ProductController | /User |
| baseRoute-relative * | Url.Action("", "~User") |
Admin.ProductController | /User |
| Application-relative | Url.Action("", "~~User") |
Admin.ProductController | /User |
* If you provide a baseRoute when calling the MapCodeRoutes method, that base route is also used as base route context. If baseRoute is null then this syntax yields the same results as the application-relative reference.