Statut 400 : The JSON value could not be converted to AppTest.Shared.Models.Developer

Question

Hi,

I've application where I try to make one-to-many relationship. the controller was created (see the post here : ef-one-to-many-to-assure-the-link-with-the-main-ta.html)
I've the DeveloperActionsController that I tested with swagger. So I received the error message.
Have you an idea how I can fix this error?

{  
  "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",  
  "title": "One or more validation errors occurred.",  
  "status": 400,  
  "traceId": "00-938ace42dd83c35b05f556b91c0a3170-c2901182370015ff-00",  
  "errors": {  
    "developer": [  
      "The developer field is required."  
    ],  
    "$.actionItems[0].developer": [  
      "The JSON value could not be converted to AppTest.Shared.Models.Developer. Path: $.actionItemsTest[0].developer | LineNumber: 12 | BytePositionInLine: 31."  
    ]  
  }  
}  

Class model :

 public partial class Developer  
    {  
        [Key]  
        public int DeveloperId { get; set; }  
        public List<ActionItem>? ActionItems{ get; set; }  
    }  
  
    public class ActionItem  
    {  
        [Key]  
        public int ActionItemId { get; set; }  
        public string? Tilte { get; set; }  
        public string? Description { get; set; }  
        public string? State { get; set; }  
        public DateTime? OpenDate { get; set; }  
        public DateTime? PlanDate { get; set; }  
        public DateTime? CloseDate { get; set; }  
  
        public int DeveloperId { get; set; }  
        public Developer? Developer { get; set; }  
    }  

Controller

[Route("api/[controller]")]
[ApiController]
public class DeveloperActionsController : ControllerBase
{
private readonly ApplicationDBContext _contexts;

    public DeveloperActionsController(ApplicationDBContext contexts)  
    {  
        this._contexts= contexts;  
    }  

    // GET: api/<DeveloperActionController>  
    [HttpGet]  
    public IEnumerable<Developert> GetDevelopersWithActions()  
    {  
        return _contexts.DeveloperTests.Include(a => a.ActionItems).ToList();  
    }  

    // GET api/<DeveloperActionController>/5  
    [HttpGet("{id}")]  
    public async Task<ActionResult<Developer>> GetDeveloperActions(int id)  
    {  
        DeveloperTest? developer = await _contexts.Developer  
            .Include(a => a.ActionItems)  
            .FirstOrDefaultAsync(d => d.DeveloperId == id);  

        if (developer == null)  
        {  
            return NotFound();  
        }  

        return Ok(developer);  
    }  

    // POST api/<DeveloperActionController>  
    [HttpPost]  
    public async Task<ActionResult<Developer>> PostAsync([FromBody] Developer developer)  
    {  
        _contexts.Developer.Add(developer);  
        await _contexts.SaveChangesAsync();  

        return CreatedAtAction(nameof(GetDeveloperActions), new { id = developer.DeveloperId }, developer);  
    }  

    // PUT api/<DeveloperActionController>/5  
    [HttpPut("{id}")]  
    public async Task<ActionResult<Developer>> Put(int id, [FromBody] ActionItem actionItem)  
    {  
        DeveloperTest? developer = await _contexts.Developer  
            .Include(a => a.ActionItems)  
            .FirstOrDefaultAsync(d => d.DeveloperId == id);  

        if (developer == null)  
        {  
            return NotFound();  
        }  

        developer.ActionItems.Add(actionItem);  
        await _contexts.SaveChangesAsync();  

        return CreatedAtAction(nameof(GetDeveloperActions), new { id = developer.DeveloperId }, developer);  

    }  

    // DELETE api/<DeveloperActionController>/5  
    [HttpDelete("{id}")]  
    public async Task<IActionResult> Delete(int id)  
    {  
        DeveloperTest? developer = await _contexts.Developer  
            .Include(a => a.ActionItems)  
            .FirstOrDefaultAsync(d => d.DeveloperId == id);  

        if (developer == null)  
        {  
            return NotFound();  
        }  

        _contexts.Remove(developer);  

        await _contexts.SaveChangesAsync();  

        return NoContent();  
    }  

}  

Answer 1

Hi, sorry for the late answer.

could you please tell us when you get this error? On loading or while sending any request?

I received this error message when I try to test POST method via swagger

Answer 2

My application is relatively heavy for testing.
So I redid a test application and I have exactly what you suggested to put a foreign key.
The controller, modelclass and ApplicationDBcontext are what I have at the beginning of this post. I also did a migration to get access to the Developers & ActionItems tables.

I added a razor page to initialize the Developers table first. Nothing happens when I do htpp request.
Plus When I added the simple for loop I the error.

Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]  
      Unhandled exception rendering component: Object reference not set to an instance of an object.  
System.NullReferenceException: Object reference not set to an instance of an object.  

Anyway when I use swagger and test Get, Post, Put, Delete I receive the status 404!!

I would really like to understand why I get this type of error when I am doing something that is actually quite simple.

@page "/test"  
@using AppTest.Shared.Models  
@using System.Text.Json  
@using System.ComponentModel  
@inject HttpClient Http  
  
<h3>TestDev</h3>  
      
<table class="table">  
        <thead>  
            <tr>  
                <th>ID</th>                                       
            </tr>  
        </thead>  
        <tbody>       
      @foreach (var dev in developer)  
        {  
            <tr>  
                <td>@dev.DeveloperId</td>                      
            </tr>  
        }           
        </tbody>  
  </table>  
  <table class="table">  
        <thead>  
            <tr>  
                <th>ID</th>  
                <th>State</th>                  
            </tr>  
        </thead>  
        <tbody>                
        </tbody>  
  </table>  
  
@code{  
    Developer[]? developer { get; set; }  
         
    protected override async Task OnInitializedAsync()  
    {  
        developer=await Http.GetFromJsonAsync<Developer[]>("api/developeractions");  
    }  
 }  

Answer 3

your issues are from using entity models as api models. in the ActionItem you are trying to post navigation values. create separate POCO request/response models for the json.

Answer 4

Hi,
I tried it in controller :

 return Ok(JsonSerializer.Serialize(developer, new JsonSerializerOptions  
            {  
                PropertyNamingPolicy = null  
            }));  

your issues are from using entity models as api models

Could you explain because I don't really understand? thanks in advance

Answer 5

I have searched the internet and I can't find (or don't quite understand the principle) a clear explanation for creating separate POCO request/response models for the json.

Could you please help me to unblock?

thanks in advance !!