NETCORE MVC - How to work with nested, multi-parameterized routes

Question

Looking for best practices when working with nested routes in .NET Core MVC.

Let's say CampusController.cs works with a base model:

[Route("api/campus/")] public class CampusController : Controller {     ...     [HttpGet]     [Route("{campusId}")]     public IActionResult GetCampusInfo ([FromQuery]int campusId) { ... } } 

And BuildingController.cs works with a child model:

[Route("api/campus/{campusId}/building")] public class BuildingController : Controller {     ...     [HttpGet]     [Route("{buildingId}")]     public IActionResult GetBuilding ([FromQuery]int buildingId) { ... }      [Route("{buildingId}/")]     public IActionResult GetBuilding ([FromQuery]int buildingId) { ... }     ....     (more Action Methods) } 

If buildingId maps directly to the database it could retrieved even if the provided campusId isn't the parent. To keep the URL clean when calling /api/campus/{campusId}/building/{buildingId} I'd like to validate {campusId} and return a 4xx coded IActionResult if it's invalid. There has to be a better way than including validation logic in every Action Method inside BuildingController.

• Is there a way to cascade multiple Action methods on different controllers? So that a validation method on CampusController would be called first and in turn call a method onBuildingController?
• Is there a way to have a controller-level verification of campusId that could short circuit and return a ActionResult if validation fails?

EDIT: When I refer to validation logic I mean API signals; not the business-logic that actually determines if campusId is/isn't valid.

Thanks in advance!

Answer 1

If using placeholder in the route prefix you would also need to include it in the action itself

[Route("api/campus/{campusId:int}/building")] public class BuildingController : Controller {     //...      [HttpGet]     [Route("{buildingId:int}")] // Matches GET api/campus/123/building/456     public IActionResult GetBuilding ([FromRoute]int campusId, [FromRoute]int buildingId) {          //... validate campus id along with building id      }     } 

If concerned about repeated code for validation then create a base controller for campus related request and have a shared validation method.

Another option is to have a service/repository that can be used to verify campus id and its relation to the provided building id if needed.

Answer 2

It sounds like you want your users to provide a campusId when talking to the BuildingController, and your BuildingController to validate campusId in a DRY kind of way.

If that's the case, you can create an input model for your BuildingController methods:

public class BuildingIdInput {    [Required]    public int? CampusId { get; set; }    [Required]    public int? BuildingId { get; set; } } 

Then you can let MVC bind user input to this model.

[Route("api/campus")] public class BuildingController : Controller {    [HttpGet]    [Route("{campusId}/building/{buildingId}")]    public IActionResult GetBuilding (BuildingIdInput input)     {        if (ModelState.IsValid)        {...}    } }