I am getting Status 500 code from POSTMAN when sending POST request to Asp.Net Core Web Api (version 3.1)

Question

I am stuck with web api testing between POSTMAN and Asp.Net Core Web Api.

It is likely that Web app responses only when it can model-binds from URL. However, it responses status 500 code every time it should model-binds from HTTP request body.

My codes are as below.

Web Api Controller code:

    [ApiController]
    [Route("api/[controller]")]
    public class OrderController : ControllerBase
    {
        private IOrderRepository _orderRepo;

        public OrderController(IOrderRepository repo) // Dependency Injection
        {
            _orderRepo = repo;
        }

        [HttpGet]
        public IEnumerable<Order> Get() => _orderRepo.Orders;

        [HttpGet("{id}")]
        public Order Get(int id) => _orderRepo[id];

        [HttpPost]
        public Order Post([FromBody] Order order) => _orderRepo.Add(order);

Model Class Code:

    public class Order
    {
        public int Id { get; set; } = 0; 
        public string ClientName { get; set; }
        public string Menu { get; set; }
        public int NoOfMenu { get; set; }

        public Order(string clientName, string menuName, int noOfMenu)
        {
            ClientName = clientName;
            Menu = menuName;
            NoOfMenu = noOfMenu;
        }
    }

Repository's code for POST action method:

        // deleted for brevity

        private Dictionary<int, Order> _orderlist = new Dictionary<int, Order>();
        
        public Order Add(Order newOrder)
        {
            if(newOrder.Id == 0)
            { 
                int key = _orderlist.Count;
                while(_orderlist.ContainsKey(key)) key++;
                newOrder.Id = key;
            }

            _orderlist[newOrder.Id] = newOrder;

            return newOrder;
        }

in POSTMAN, Get request was successful.

This is when Get: api/Order

This is when Get: api/Order/id

However, Post request returns Status 500.

Can anybody help for this situation?

Answer 1

I test your codes and reproduced your problem. You can add a parameterless constructor.

public class Order
{
    public int Id { get; set; } = 0;
    public string ClientName { get; set; }
    public string Menu { get; set; }
    public int NoOfMenu { get; set; }

    public Order(string clientName, string menuName, int noOfMenu)
    {
        ClientName = clientName;
        Menu = menuName;
        NoOfMenu = noOfMenu;
    }
    public Order()
    {

    }
}