Error when send POST to a function with defined route - Web API 2

Question

I have this function in my Web Service that add a 'addlocalidade' in my table TBLocalidade in SQL Server.

[HttpPost]
[Route("api/insertlocalidade")]
[ResponseType(typeof(TBLocalidade))]
public async Task<IHttpActionResult> insertlocalidade([FromBody] TBLocalidade addlocalidade)
{
    objapi.Configuration.LazyLoadingEnabled = false;
    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }
    objapi.TBLocalidade.Add(addlocalidade);
    await objapi.SaveChangesAsync();

    return CreatedAtRoute("DefaultApi", new { id = addlocalidade.idLocalidade }, addlocalidade);
}

If I remove the route, it works perfectly, but when I add this route: [Route("api/insertlocalidade")], it doesn't work good, I tested it with httpRequester, it was possible to add the value in database, but it return this error message:

{"Message":"An error has occurred.","ExceptionMessage":"UrlHelper.Link must not return null.","ExceptionType":"System.InvalidOperationException","StackTrace":" em System.Web.Http.Results.CreatedAtRouteNegotiatedContentResult1.Execute()\r\n em System.Web.Http.Results.CreatedAtRouteNegotiatedContentResult1.ExecuteAsync(CancellationToken cancellationToken)\r\n em System.Web.Http.Controllers.ApiControllerActionInvoker.d__0.MoveNext()\r\n--- Fim do rastreamento de pilha do local anterior onde a exceção foi gerada ---\r\n em System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n em System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n em System.Web.Http.Controllers.ActionFilterResult.d__2.MoveNext()\r\n--- Fim do rastreamento de pilha do local anterior onde a exceção foi gerada ---\r\n em System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n em System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n em System.Web.Http.Controllers.AuthenticationFilterResult.d__0.MoveNext()\r\n--- Fim do rastreamento de pilha do local anterior onde a exceção foi gerada ---\r\n em System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n em System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n em System.Web.Http.Dispatcher.HttpControllerDispatcher.d__1.MoveNext()"}

Anyone can please help me to solve this error?

Answer 1

That is because there is not enough information for the UrlHelper to generate the link using convention based routing.

Assuming a web api config like this ...

public static class WebApiConfig {
    public static void Register(HttpConfiguration config) {
        // Attribute routing.
        config.MapHttpAttributeRoutes();

        // Convention-based routing.
        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );
    }
}

You would need to provide the controller name when generating the created at response using that route.

return CreatedAtRoute("DefaultApi", new { controller = "localidade", id = addlocalidade.idLocalidade }, addlocalidade);

However since you are using an attribute routing then, assuming the following get action in the controller ...

//GET api/localidade/5
[HttpGet]
[Route("api/localidade/{id:int}")]
[ResponseType(typeof(TBLocalidade))]
public async Task<IHttpActionResult> getlocalidade(int id) { ... }

You have to add a route name to the route attribute which is used by the UrlHelper for generating links.

//GET api/localidade/5
[HttpGet]
[Route("api/localidade/{id:int}", Name="GetLocalidade")] // <-- NOTE THE CHANGE
[ResponseType(typeof(TBLocalidade))]
public async Task<IHttpActionResult> getlocalidade(int id) { ... }

and use it in the CreatedAtRoute in order to generate the link properly

return CreatedAtRoute("GetLocalidade", new { id = addlocalidade.idLocalidade }, addlocalidade);