I’ve this situation:

server side:

[ApiController]
[Route("[controller]")]
public class TestController : Controller
{
    [HttpPost]
    public IActionResult Action(byte[] value)
    {
        var jsonString = Encoding.UTF8.GetString(value);
        var myObject = JsonSerializer.Deserialize<SampleObject>(jsonString);

        return Ok(myObject);
    }
}

Client:

public static class Program
{
    public static async Task Main(string[] args)
    {
        await SendObjectAsync();
    }
    
    private static  async Task SendObjectAsync()
    {
        var myObject = new SampleObject();

        var jsonString = JsonSerializer.Serialize(myObject);
        var byteArray = Encoding.UTF8.GetBytes(jsonString);

        using var client = new HttpClient();
    
        var content = new ByteArrayContent(byteArray);
    
        content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");

        var response = await client.PostAsync("http://localhost:5287/Main", content);

        if (response.IsSuccessStatusCode)
        {
            var responseData = await response.Content.ReadAsStringAsync();
            var returnedObject = JsonSerializer.Deserialize<SampleObject>(responseData);

            Console.WriteLine($"Received: {returnedObject!.Text},{returnedObject.Number}");
        }
    }
}

In the response i get always this error:

StatusCode: 415, ReasonPhrase: 'Unsupported Media Type', Version: 1.1, Content: System.Net.Http.HttpConnectionResponseContent, Headers:
{
  Date: Fri, 16 Aug 2024 21:48:40 GMT
  Server: Kestrel
  Transfer-Encoding: chunked
  Content-Type: application/problem+json; charset=utf-8
}, Trailing Headers:
{
}

I also tried to add the FromBody attribute in the Action params, but without success.

Can someone please explain? I want to send binary raw data.

Thanks.