Web Api Post ActionResult not Returning object

Question

I can do the [HttpGet] and [HttpGet("{id}")] requests fine. But when I do [HttpPost], I'm running into problems. I'm using postman to validate the http requests. I haven't setup a database yet, and am just using an api with models for now. Here is the code structure...

controller.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using CoreStudyApi.OutgoingObjects;
using CoreStudyApi.Api;
using CoreStudyApi.IncomingObjects;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;

namespace CoreStudyApi.Controllers
{
    [Route("people")]
    [ApiController]
    [Produces("application/json")]
    public class PeopleController : Controller
    {
        private People_API P_API = new People_API();

        [HttpGet]
        public IActionResult Get()
        {
            var Result = P_API.GetPeople().ToList(); // Cannot pass Dictionary over httprequest, must convert to list or string.
            //var Result = "test";
            /*var Result = new List<string>()
            {
                "one",
                "two",
                "three"
            };*/
            return Ok(Result);
        }

        [HttpGet("{id}")]
        [ProducesResponseType(StatusCodes.Status200OK)]
        [ProducesResponseType(StatusCodes.Status404NotFound)]
        public IActionResult Get(int Id)
        {
            try
            {
                var Result = P_API.GetPersonNameById(Id);
                return Ok(Result);
            } catch(Exception e)
            {
                return NotFound(e.Message);
                // return NotFound("User not found");
                // return NotFound();
            }

        }

        [HttpPost]
        [ProducesResponseType(StatusCodes.Status201Created)]
        [ProducesResponseType(StatusCodes.Status400BadRequest)]
        public ActionResult<Person> Post([FromBody] PersonName NameObject)
        {
            string Name = NameObject.Name;
            if(string.IsNullOrWhiteSpace(Name))
            {
                return BadRequest();
            }

            Person NewPerson = P_API.AddPerson(Name);

            return CreatedAtAction("Created", new { id = NewPerson.Id, name = NewPerson.Name }, NewPerson);
        }
    }
}

I can see the Person object was created successfully (using visual studio debugger) and has the values of an Id to 6 and a Name to "scrappy", but the problem hits when I try to do the return.

People_API.cs

using CoreStudyApi.OutgoingObjects;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using CoreStudyApi.Models;

namespace CoreStudyApi.Api
{
    public class People_API
    {
        // Variables
        private People P_Model = new People();

        // Helper Functions
        private int GetNextUnusedPeopleId()
        {
            for(int NewId = 1; NewId < P_Model.PeopleRecords.Count(); NewId++)
            {
                if (!P_Model.PeopleRecords.ContainsKey(NewId))
                {
                    return NewId;
                }
            }
            return P_Model.PeopleRecords.Count() + 1;
        }
        // Private Functions
        private Dictionary<int, string> GetPeopleFromData()
        {
            return P_Model.PeopleRecords;
        }
        private string GetPersonNameByIdFromData(int Id)
        {
            if (!P_Model.PeopleRecords.ContainsKey(Id))
            {
                return "Not Found";
            }
            return P_Model.PeopleRecords[Id];
        }
        private Person AddPersonToData(string Name)
        {
            // Get the next available Id
            int NewId = GetNextUnusedPeopleId();
            // Add the new person to the data
            P_Model.PeopleRecords.Add(NewId, Name);
            // Check to see if the new person was added and store as an object
            Person NewPerson = new Person(NewId, P_Model.PeopleRecords[NewId]);
            // Return the person added in the form of a person object
            return NewPerson;
        }
        // Public Functions
        public Dictionary<int, string> GetPeople()
        {
            return GetPeopleFromData();
        }
        public string GetPersonNameById(int Id)
        {
            return GetPersonNameByIdFromData(Id);
        }
        public Person AddPerson(string Name)
        {
            return AddPersonToData(Name);
        }
    }
}

PersonName.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace CoreStudyApi.IncomingObjects
{
    public class PersonName
    {
        public string Name { get; set; }
    }
}

People.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace CoreStudyApi.Models
{
    public class People
    {
        public Dictionary<int, string> PeopleRecords = new Dictionary<int, string>()
        {
            { 1, "shaggy" },
            { 2, "fred" },
            { 3, "velma" },
            { 4, "daphne" },
            { 5, "scooby" }
        };
    }
}

Person.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Threading.Tasks;

namespace CoreStudyApi.OutgoingObjects
{
    public class Person
    {
        public int Id { get; set; }
        [Required]
        public string Name { get; set; }

        // Constructor
        public Person(int Id, string Name)
        {
            this.Id = Id;
            this.Name = Name;
        }
    }
}

The problem code snippet...

[HttpPost]
[ProducesResponseType(StatusCodes.Status201Created)]
[ProducesResponseType(StatusCodes.Status400BadRequest)]
public ActionResult<Person> Post([FromBody] PersonName NameObject)
{
    string Name = NameObject.Name;
    if(string.IsNullOrWhiteSpace(Name))
    {
        return BadRequest();
    }
     Person NewPerson = P_API.AddPerson(Name); // Debugger confirms object was created successfully
     // Fails to return here
     return CreatedAtAction("Created", new { id = NewPerson.Id, name = NewPerson.Name }, NewPerson);
}

Receives the following with postman:

Updated Per Request:

Postman Output

System.InvalidOperationException: No route matches the supplied values.
   at Microsoft.AspNetCore.Mvc.CreatedAtActionResult.OnFormatting(ActionContext context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ObjectResultExecutor.ExecuteAsyncCore(ActionContext context, ObjectResult result, Type objectType, Object value)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ObjectResultExecutor.ExecuteAsync(ActionContext context, ObjectResult result)
   at Microsoft.AspNetCore.Mvc.ObjectResult.ExecuteResultAsync(ActionContext context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultAsync(IActionResult result)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeNextResultFilterAsync[TFilter,TFilterAsync]()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|19_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

HEADERS
=======
Accept: */*
Accept-Encoding: gzip, deflate
Cache-Control: no-cache
Connection: keep-alive
Content-Length: 22
Content-Type: application/json
Host: localhost:44325
User-Agent: PostmanRuntime/7.21.0
Postman-Token: 33b94ca5-5a81-451c-9221-380d27a17536

Answer 1

Return the Person object directly instead of returning CreatedAtAction.

    [HttpPost]
    [ProducesResponseType(StatusCodes.Status201Created)]
    [ProducesResponseType(StatusCodes.Status400BadRequest)]
    public ActionResult<Person> Post([FromBody] PersonName NameObject)
    {
        string Name = NameObject.Name;
        if (string.IsNullOrWhiteSpace(Name))
        {
            return BadRequest();
        }
        Person NewPerson = P_API.AddPerson(Name); // Debugger confirms object was created successfully
                                                  // Fails to return here
        return NewPerson; //  CreatedAtAction("Created", new { id = NewPerson.Id, name = NewPerson.Name }, NewPerson);
    }

Answer 2

It looks to me like the issue you are experiencing occurs after the POST has executed.

Here is the signature for the method you use to return, according to the documentation:

[Microsoft.AspNetCore.Mvc.NonAction]
public virtual Microsoft.AspNetCore.Mvc.CreatedAtActionResult CreatedAtAction (string actionName, object routeValues, object value);

The method creates an instance of type CreatedAtActionResult which returns a response with a Location header constructed using the parameters you pass. For 201 responses, this header represents the URL to the newly created resource (where you can find it).

I don't see an Action method called Created in your code. I think it's trying to construct the Url using "created" and new { id = NewPerson.Id, name = NewPerson.Name } and it can't find a matching route, so it fails.

Change the return line to this:

return CreatedAtAction("Get", new { id = NewPerson.Id }, NewPerson);

This should result in a route that matches the existing method public IActionResult Get(int Id).