Why is my attribute routing not working?

Question

This is what my controller looks like:

[Route("api/[controller]")]
[Produces("application/json")]
public class ClientsController : Controller
{
    private readonly IDataService _clients;

    public ClientsController(IDataService dataService)
    {
        _clients = dataService;
    }

    [HttpPost]
    public int Post([Bind("GivenName,FamilyName,GenderId,DateOfBirth,Id")] Client model)
    {
        // NB Implement.
        return 0;
    }

    [HttpGet("api/Client/Get")]
    [Produces(typeof(IEnumerable<Client>))]
    public async Task<IActionResult> Get()
    {
        var clients = await _clients.ReadAsync();
        return Ok(clients);
    }

    [HttpGet("api/Client/Get/{id:int}")]
    [Produces(typeof(Client))]
    public async Task<IActionResult> Get(int id)
    {
        var client = await _clients.ReadAsync(id);
        if (client == null)
        {
            return NotFound();
        }

        return Ok(client);
    }

    [HttpGet("api/Client/Put")]
    public void Put(int id, [FromBody]string value)
    {
    }

    [HttpGet("api/Client/Delete/{id:int}")]
    public void Delete(int id)
    {
    }
}

Yet when I request the URL /api/Clients/Get, as follows:

json = await Client.GetStringAsync("api/Clients/Get");

I get back the following exception:

AmbiguousActionException: Multiple actions matched. The following actions matched route data and had all constraints satisfied:

Assessment.Web.Controllers.ClientsController.Index (Assessment.Web) Assessment.Web.Controllers.ClientsController.Details (Assessment.Web) Assessment.Web.Controllers.ClientsController.Create (Assessment.Web)

Client is an HttpClient. Please note that no GET action matched the route data, despite the same name, id.

What could be wrong here?

Answer 1

You are using the attributes wrong.

You have a route on the controller

[Route("api/[controller]")]

which would map to api/Clients and prefix that to any action routes in the controller.

So that means that

[HttpGet("api/Client/Get")] // Matches GET api/Clients/api/Client/Get
[Produces(typeof(IEnumerable<Client>))]
public async Task<IActionResult> Get()
{
    var clients = await _clients.ReadAsync();
    return Ok(clients);
}

Matches a GET to api/Clients/api/Client/Get because of the route prefix on the controller.

Referencing Routing to Controller Actions

You need to update the attribute routes on the actions accordingly

[Route("api/[controller]")]
[Produces("application/json")]
public class ClientsController : Controller {
    private readonly IDataService _clients;

    public ClientsController(IDataService dataService)
    {
        _clients = dataService;
    }

    [HttpPost] //Matches POST api/Clients
    public int Post([Bind("GivenName,FamilyName,GenderId,DateOfBirth,Id")] Client model) {
        // NB Implement.
        return 0;
    }

    [HttpGet("Get")] //Matches GET api/Clients/Get
    [Produces(typeof(IEnumerable<Client>))]
    public async Task<IActionResult> Get() {
        //...code removed for brevity
    }

    [HttpGet("Get/{id:int}")] //Matches GET api/Clients/Get/5
    [Produces(typeof(Client))]
    public async Task<IActionResult> Get(int id) {
        //...code removed for brevity
    }

    [HttpGet("Put")] //Matches PUT api/Clients/Put
    public void Put(int id, [FromBody]string value) {
        //...code removed for brevity
    }

    [HttpGet("Delete/{id:int}")] //Matches GET api/Clients/Delete/5
    public void Delete(int id) {
    }
}

The delete action should actually be refactored to a HTTP DELETE and should return a IActionResult

[HttpDelete("Delete/{id:int}")] //Matches DELETE api/Clients/Delete/5
public IActionResult Delete(int id) {
    //...code removed for brevity
}