ASP.NET Core Controllers Route attribute inheritance and Abstract controllers actions - AmbiguousActionException

Question

I'm working on ASP.NET Core Webapi project. I would like to implement some kind of Base/Abstract generic controller for all methods that are common for every controller (e.g. CRUD methods) and inherit this Controller in all other controllers. I attach example code below:

public abstract class BaseApiController : Controller { [HttpGet] [Route("")] public virtual IActionResult GetAll() { ... } [HttpGet] [Route("{id}")] public virtual IActionResult GetById(int id) { ... } [HttpPost] [Route("")] public virtual IActionResult Insert(myModel model) { ... } } [Route("api/Student")] public class StudentController : BaseApiController { // Inherited endpoints: // GetAll method is available on api/Student [GET] // GetById method is available on api/Student/{id} [GET] // Insert method is available on api/Student [POST] // // Additional endpoints: // ShowNotes is available on api/Student/{id}/ShowNotes [GET] [HttpGet] [Route("{id}/ShowNotes")] public virtual IActionResult ShowNotes(int id) { ... } } [Route("api/Teacher")] public class TeacherController : BaseApiController { // Inherited endpoints: // GetAll method is available on api/Teacher [GET] // GetById method is available on api/Teacher/{id} [GET] // Insert method is available on api/Teacher [POST] // // Additional endpoints: // ShowHours is available on api/Teacher/{id}/ShowHours [GET] [HttpGet] [Route("{id}/ShowHours")] public virtual IActionResult ShowHours(int id) { ... } }

I have seen this kind of solution in .NET Framework WebApi, with additional custom RouteProvider, e.g.:

public class WebApiCustomDirectRouteProvider : DefaultDirectRouteProvider { protected override IReadOnlyList<IDirectRouteFactory> GetActionRouteFactories(HttpActionDescriptor actionDescriptor) { return actionDescriptor.GetCustomAttributes<IDirectRouteFactory>(inherit: true); } }

Every time I try to reach Endpoint in derived controller I got AmbiguousActionException:

Multiple actions matched. The following actions matched route data and had all constraints satisfied: XXX.WebApi.Controllers.CommonAppData.TeacherController.GetById XXX.WebApi.Controllers.CommonAppData.StudentController.GetById

Is it possible to create such Base controller in .NET Core WebApi? How should I write it to reach Action Methods without declaring it explicitly in derived Controller? How should I configure this kind of solution? Any additional configuration in Startup class?

Your code works fine in .NET Core WebAPI without any additional custom RouteProvider. Where is the problem? — Roman Marusyk
– Roman Marusyk, Commented Nov 26, 2018 at 20:17
Yes you can achieve this for CRUD operations and catching exceptions and logging. BaseController is helpful for corss-cutting cuncerns in your application. I would create a generic base controller ... public class BaseController<T> where T will be your model for Teacher and Student types. — Yawar Murtaza
– Yawar Murtaza, Commented Nov 26, 2018 at 20:19
Also, the routing in .net core is attribute based. There is no route.config file. — Yawar Murtaza
– Yawar Murtaza, Commented Nov 26, 2018 at 20:20
I edited the question :) I receive AmbiguousActionException for every derived endpoint. My Base controller is Generic, but for more "clear" question I skipped this part. — Piotr Trojan
– Piotr Trojan, Commented Nov 26, 2018 at 20:21

Ali Mahmoodi · Accepted Answer · 2022-10-02 09:05:30Z

As this topic is a good one so it worth and I explain how I did it. You can create a Generic Controller like this :

[Route("api/[controller]/[action]")] [ApiController] public class BaseController<TEntity> : Controller where TEntity : class, new() { private readonly YourDbContext _db; public BaseController(YourDbContext db) { _db=db; } public virtual async Task<IActionResult> GetAll() { var data= await _db.Set<TEntity>().ToListAsync(); return View(data); } public virtual IActionResult GetById(int id) { var data= await _db.Set<TEntity>().FindAsync(e=>e.Id == id); return View(data); } ..... }

Then you can use it like this :

public class StudentController : BaseController<Student> { }

Off course you can write it better with optional parameters something like this:

public virtual async Task<IActionResult> GetAll(Expression<Func<TEntity, bool>>? predicate = null) { var data= await _db.Set<TEntity>().Where(predicate).ToListAsync(); .... }

Or even override every action in inherited controller as you like and adding necessary parameters to your actions

public override Task<IActionResult> Get(....

I hope enjoy it ;) and don't forget to up Vote .

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