ASP.NET core - how to pass optional [FromBody] parameter?

Question

How do I pass optional (nullable) [FromBody] parameter in ASP.NET Core (5.0)? If I don't send body in my request I get 415 Unsupported Media Type error. Can this be configured and if so, how to do it on a controller or action, rather than an app level? I presume it has to do something with model validation, but not sure. Thanks.

[HttpGet("[action]")]
public async Task<IActionResult> GetElementsAsync([FromBody] IEnumerable<int> elements = default)
{
  var result = await dataService.GetData(elements);
  return Ok(result);
}

EDIT: To clarify:

This is typical scenario and it works normally:

But passing empty body is returning 415 right away without even reaching action:

Answer 1

Just add content-type in your request header. Without the content-type:application/json will appear 415 when body is empty.

No changes to your controller. Test in my side is ok.

I created a new asp.net core 5 api project and this is my controller:

using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;

namespace WebApi_net5.Controllers
{
    public class HomeController : ControllerBase
    {
        [HttpGet("[action]")]
        public string GetElementsAsync([FromBody] IEnumerable<int> elements = default)
        {
            return "value";
        }
    }
}